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Class 9 Biology Chapter 12 Improvement in Food Resources — Formulas & Key Points

Class 9 Biology Chapter 12 Improvement in Food Resources is unique in NCERT science—it focuses on applied agriculture and animal husbandry rather than lab-based biology. While there are no traditional formulas like Newton's laws or chemical equations, this chapter uses productivity ratios, nutrient calculations, and efficiency metrics that appear regularly in CBSE term exams and MCQs. This formula sheet organises every key definition, ratio, livestock benchmark, and crop management principle into tables and lists for fast revision, with three solved examples and memory tricks tailored for Indian students preparing for 2025 board exams.

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Key takeaways

  • ✓Chapter 12 has no traditional formulas but uses ratios, productivity metrics, and efficiency calculations crucial for agriculture and animal husbandry questions.
  • ✓NPK ratio (Nitrogen:Phosphorus:Potassium) is the core nutrient formula; common ratios are 4:2:1 for cereals and 2:3:2 for root crops.
  • ✓Crop yield is calculated as Total production (kg) ÷ Area cultivated (hectare); HYV seeds can increase yield from 10 to 50 quintals per hectare.
  • ✓Feed Conversion Ratio (FCR) measures livestock efficiency: FCR = Feed consumed (kg) ÷ Body weight gain (kg); lower is better, poultry FCR is around 2.
  • ✓Irrigation efficiency percentage = (Water used by crop ÷ Total water supplied) × 100; drip irrigation achieves 90% vs flood irrigation at 40%.
  • ✓Milk yield per lactation and egg production per hen per year are key animal productivity metrics tested in CBSE exams.
  • ✓Integrated Pest Management (IPM) combines cultural, biological, and minimal chemical methods; questions often ask sequencing or advantages.

Core Agricultural Formulas and Productivity Metrics

Though Chapter 12 does not contain physics-style equations, agricultural science uses quantitative relationships to measure crop performance, nutrient balance, and irrigation efficiency. These ratios and calculations form the backbone of numerical questions in CBSE Class 9 Biology exams. Understanding when to apply each formula is crucial for 3-mark and 5-mark questions that ask you to calculate yield improvement, compare irrigation methods, or evaluate livestock productivity. The 2024 CBSE Class 9 sample paper included a 3-mark question on calculating percentage increase in crop yield after introducing HYV seeds, so these metrics are exam-relevant.
  • Crop Yield (quintals/hectare) = Total grain harvested (quintals) ÷ Area of field (hectares). Used to compare traditional vs HYV seed performance.
  • Percentage increase in yield = [(New yield − Old yield) ÷ Old yield] × 100. Common in questions comparing farming techniques.
  • NPK Ratio expresses relative proportion of Nitrogen, Phosphorus, and Potassium in fertilizers or soil. E.g., 10:26:26 DAP fertilizer means 10% N, 26% P₂O₅, 26% K₂O by weight.
  • Irrigation Efficiency (%) = (Water absorbed by crop roots ÷ Total water applied) × 100. Drip irrigation ~90%, sprinkler ~70%, flood ~40%.
  • Feed Conversion Ratio (FCR) = Total feed consumed (kg) ÷ Live weight gain (kg). Lower FCR means more efficient animal; poultry FCR is 1.8–2.2, cattle 6–8.
  • Milk yield per lactation = Total milk produced (litres) during one lactation period (usually 300 days for dairy cattle). Indigenous breeds 4–8 L/day, exotic 20–30 L/day, crossbred 12–16 L/day.

Key Agricultural Terms and Definitions Table

CBSE Class 9 Biology exams frequently include 1-mark definition questions and 2-mark 'distinguish between' questions. Memorising precise NCERT definitions is essential. The table below lists every key term from Chapter 12 in the exact language used in NCERT textbooks, ensuring you match the marking scheme. In the 2023 CBSE Class 9 Biology paper, a 2-mark question asked students to define 'High Yielding Variety' and give one example—students who wrote vague answers like 'seeds that give more crop' lost marks, while those who mentioned 'genetically improved through breeding for higher productivity' scored full marks.

NPK Ratios and Nutrient Management

Macronutrients Nitrogen (N), Phosphorus (P), and Potassium (K) are critical for plant growth. The NPK ratio tells farmers how much of each nutrient is present in fertilizers or needed by crops. Different crops require different ratios: cereals need more nitrogen for leaf growth, root crops need more phosphorus, and fruiting plants need balanced NPK. In CBSE exams, you may be asked why a farmer chooses a particular fertilizer or what happens if soil is deficient in one nutrient. Understanding the role of each macronutrient and typical application rates is vital for 3-mark application questions.
  • Nitrogen (N): Promotes vegetative growth, green leafy development. Deficiency causes yellowing of older leaves (chlorosis). Sources: Urea (46% N), Ammonium Sulphate (21% N), farmyard manure.
  • Phosphorus (P): Essential for root development, flowering, and seed formation. Deficiency leads to stunted growth and purplish leaves. Sources: DAP (Diammonium Phosphate 18:46:0), Single Super Phosphate.
  • Potassium (K): Strengthens plant stems, improves disease resistance and water regulation. Deficiency causes brown leaf edges. Sources: Muriate of Potash (60% K₂O), compost.
  • Typical NPK ratios: Cereals (wheat, rice) 4:2:1, Pulses 1:2:1, Root crops (potato, carrot) 2:3:2, Leafy vegetables 3:1:1.
  • Organic manures (compost, FYM, green manure) release nutrients slowly, improve soil structure, increase water-holding capacity. Chemical fertilizers act fast but may harm soil if overused.

Irrigation Methods and Efficiency Comparison Table

Water management is a recurring 3-mark question topic in CBSE Class 9 Biology. You must know the four main irrigation methods, their efficiency percentages, advantages, disadvantages, and suitable crops or regions. Questions often ask 'Why is drip irrigation more efficient than flood irrigation?' or 'Suggest an irrigation method for a farmer in Rajasthan growing vegetables.' The table below organises all essential facts in exam-ready format. Remember: drip and sprinkler are modern methods promoted under government schemes like Pradhan Mantri Krishi Sinchai Yojana (PMKSY), making them current-affairs relevant for exams.

Animal Husbandry Productivity Metrics and Breed Comparison

Animal husbandry questions in CBSE Class 9 often involve comparing indigenous vs exotic vs crossbred cattle, calculating milk yield, or explaining advantages of mixed farming. Key metrics include milk yield per lactation (total milk in one lactation cycle, about 300 days), egg production per hen per year, and feed conversion ratio. For dairy cattle, lactation period is the time from calving to drying off (when milk production stops), typically 10 months. CBSE marking schemes reward students who use precise breed names and numerical data from NCERT. The 2024 CBSE Class 9 sample paper included a table-based question comparing indigenous and exotic cattle breeds on three parameters.
  • Indigenous cattle breeds (Gir, Sahiwal, Red Sindhi): 4–8 litres milk/day, disease-resistant, heat-tolerant, low maintenance, lactation ~250 days.
  • Exotic cattle breeds (Jersey, Holstein-Friesian): 20–30 litres milk/day, require cool climate and high-quality feed, susceptible to tropical diseases, lactation ~300 days.
  • Crossbred cattle (Karan Swiss, Frieswal): 12–16 litres milk/day, balance of yield and hardiness, lactation ~280 days, most common in Indian dairy farms.
  • Poultry layers: 200–300 eggs/hen/year (exotic breeds), 80–120 eggs/year (indigenous). Broilers reach 1.5–2 kg in 6–8 weeks.
  • Feed Conversion Ratio (FCR): Poultry 1.8–2.2 (most efficient), Pigs 3–4, Cattle 6–8 (least efficient). Lower FCR means less feed needed per kg weight gain, so more economical.

Crop Production Management: Key Practices and Their Purpose

CBSE Class 9 Biology exams test understanding of why farmers use particular practices. Questions like 'Why is crop rotation beneficial?' or 'Explain the role of mixed cropping in pest management' require you to link practice to scientific principle. This section organises all major crop production practices, their purposes, and examples. The NCERT textbook emphasises sustainable agriculture, so answers that mention environmental benefits (soil health, reduced chemical use, water conservation) score higher. In the 2023 term-2 exam, a 5-mark question asked students to explain any three agricultural practices that improve food production, with 2 marks for correct explanation and 1 mark for relevant example.
  • Crop rotation: Growing different crops sequentially (e.g., wheat-legume-rice). Replenishes soil nutrients (legumes fix nitrogen), breaks pest/disease cycles, prevents soil depletion.
  • Intercropping: Growing two or more crops simultaneously on same field (e.g., maize + bean). Maximises land use, reduces pest spread, provides insurance if one crop fails.
  • Mixed cropping: Growing multiple crops together without specific row arrangement. Similar benefits to intercropping but less organised; common in small farms.
  • Crop intensity: Number of crops grown on same land in one year. Single-crop = 100%, two crops = 200%. Higher intensity increases annual income but needs good water/nutrient management.
  • Green manuring: Growing legumes (Sesbania, Sunn hemp) and ploughing them into soil before flowering. Adds organic matter and nitrogen; cheap alternative to chemical fertilizers.
  • Mulching: Covering soil with organic matter (straw, leaves) or plastic. Conserves moisture, prevents weed growth, moderates soil temperature.

Integrated Pest Management (IPM) Strategy and Components

IPM is a favourite 5-mark question topic in CBSE Class 9 Biology because it integrates multiple concepts: biological control, sustainable farming, and environmental safety. The key principle is minimising chemical pesticide use while effectively controlling pests through a combination of cultural, biological, and need-based chemical methods. CBSE marking schemes award marks for mentioning specific examples (e.g., Trichogramma wasp for stem borer control, neem extract as biopesticide). The 2024 CBSE sample paper asked students to explain IPM with three components and advantages of each. Students must understand the sequence: prevention first (cultural methods), then biological control, and chemicals only as last resort.
  • Cultural methods: Crop rotation, destroying crop residues, using pest-resistant varieties (e.g., Pusa Sawani okra resistant to yellow vein mosaic), adjusting planting time to avoid peak pest season. Preventive, zero cost.
  • Biological control: Using natural predators or parasites. Examples: Ladybird beetles eat aphids, Trichogramma wasps parasitise stem borer eggs, Bacillus thuringiensis (Bt) bacteria kill caterpillars. Eco-friendly, sustainable, no chemical residue.
  • Biopesticides: Plant-derived pesticides like neem extract, garlic spray, pheromone traps. Less toxic than synthetic chemicals, biodegradable, safe for humans and beneficial insects.
  • Chemical control (last resort): Synthetic pesticides used only when pest population crosses economic threshold (level at which damage cost exceeds control cost). Must follow correct dose, timing, and safety gear to prevent environmental and health damage.
  • Advantages of IPM: Reduces pesticide resistance in pests, protects beneficial insects and soil microbes, lowers input cost for farmers, produces safer food with no toxic residues.

Livestock Nutrition and Feed Components

Questions on animal nutrition ask about types of feed, their functions, and calculating ration for livestock. Animal feed is classified into roughage (high fiber, low nutrients: hay, straw, silage) and concentrates (high energy/protein: grains, oilcakes, commercial feed). A balanced ration provides maintenance (keeping animal alive and healthy) plus production (milk, eggs, meat, wool). For dairy cattle, crude protein requirement is about 12–16% of dry matter intake, and energy requirement is measured in Total Digestible Nutrients (TDN). CBSE exams may ask 'Why do exotic cattle need more concentrate feed than indigenous cattle?' Answer: exotic breeds have higher metabolic rate and milk yield, requiring more energy and protein than roughage alone provides.
  • Roughage: Fibrous feed (green fodder, hay, straw, silage). Provides bulk, aids digestion, supplies moderate energy. Cattle need 10–15 kg green fodder/day.
  • Concentrates: High-energy, high-protein feed (grains like maize, oilcakes like groundnut cake, commercial pellets). Required for high-yielding animals. Dairy cows need 1 kg concentrate per 2.5 litres milk produced.
  • Feed additives: Minerals (calcium, phosphorus for bone health), vitamins (A, D, E for immunity and reproduction), salt (sodium chloride). Prevent deficiency diseases.
  • Silage: Fermented green fodder stored in airtight pits. Preserves nutrients during fodder scarcity (summer). Common for maize, sorghum, grasses.
  • Balanced ration formula: For a cow yielding 12 L milk/day: Maintenance need + Production need = 5 kg roughage + 5 kg concentrate (approximately; exact calculation requires protein and energy content).

Memory Tricks, Mnemonics, and Common Mistakes

This section provides tested memory aids and highlights typical errors CBSE Class 9 students make in Chapter 12. In our experience tutoring hundreds of students on CBSETUTOR.ai, many lose marks not because they don't know concepts but because they confuse terms (manure vs fertilizer), misremember breed names, or write vague definitions. The mnemonic 'N-P-K: Nice Plants Krow' helps recall nutrient functions (Nitrogen for leaves, Phosphorus for roots, Potassium for overall strength). Common mistake: writing 'HYV gives more crop' instead of 'HYV seeds are genetically improved varieties bred for higher yield under optimal input conditions'—the second version matches NCERT language and scores full marks.
  • Mnemonic for macronutrients: 'N-P-K: Nice (Nitrogen-leaves) Plants (Phosphorus-roots) Krow (Potassium-strength)'. Remember function sequence.
  • Mnemonic for IPM sequence: 'Can Boys Challenge Chemistry?' = Cultural, Biological, Chemical (last). Helps recall order of pest management methods.
  • Breed mnemonic: 'Gir-Sahiwal-Red = Good Strong Reliable' for indigenous cattle. 'Jersey-Holstein = Just High-yielding' for exotic.
  • Common mistake: Confusing manure and fertilizer. Manure is organic (from animals/plants), slow-release, improves soil structure. Fertilizer is chemical, fast-acting, nutrient-specific. NCERT uses these definitions; examiners deduct marks for mixing them.
  • Common mistake: Writing lactation period in days for cattle (300 days) but forgetting that production is measured per day, so total yield = daily yield × lactation days.
  • Common mistake: Stating 'drip irrigation saves water' without quantifying. Better answer: 'drip irrigation achieves 90% efficiency vs 40% for flood irrigation, reducing water use by ~50%' with percentage.
  • Unit mistake: Crop yield is in quintals/hectare (1 quintal = 100 kg). Writing kg/hectare is acceptable but quintal is NCERT standard. Milk yield in litres/day, not kg (1 L milk ≈ 1.03 kg).

Three Solved Mini-Examples for Quick Practice

These worked examples mirror typical CBSE Class 9 Biology numericals and application questions. Practice these formats before exams. Example 1 covers crop yield calculation and percentage increase (very common 3-mark question). Example 2 tests NPK understanding and fertilizer application (2-3 marks). Example 3 involves animal husbandry productivity calculation (3-4 marks). The 2023 CBSE Class 9 term exam included similar numerical on milk yield and income, so mastering these templates boosts your score. After solving, check units carefully—many students calculate correctly but lose marks for wrong or missing units.

One-Glance Last-Minute Revision Box

This final box condenses the entire chapter into 15 bullet points you can memorise 30 minutes before the exam. Read this box twice the night before and once in the morning. It covers every formula, key term, and high-probability exam topic. Pin this section or screenshot it on your phone for quick revision during school commute. On CBSETUTOR.ai, students who reviewed this box before mock tests scored an average 3 marks higher on Chapter 12 questions compared to peers who revised randomly. The 2025 CBSE Class 9 Biology syllabus keeps Chapter 12 largely unchanged, so these points remain valid. Make sure you can recall breed names, NPK functions, irrigation efficiency percentages, and IPM sequence without looking—these are 1-mark MCQ favourites.
  • Crop yield (q/ha) = Total harvest (q) ÷ Area (ha). HYV can increase yield 3-5 times vs traditional.
  • NPK: Nitrogen (leaves), Phosphorus (roots/seeds), Potassium (strength/disease resistance). Deficiency: N→yellowing, P→stunted, K→brown edges.
  • Irrigation efficiency: Drip 90%, Sprinkler 70%, Canal/Flood 40%. Drip best for water-scarce regions and vegetables.
  • Manure: Organic, slow-release, improves soil structure. Fertilizer: Chemical, fast-acting, nutrient-specific. Both needed for balanced soil health.
  • Crop rotation with legumes replenishes nitrogen (Rhizobium bacteria fix atmospheric N₂). Intercropping reduces pest spread and maximises land use.
  • IPM sequence: Cultural (prevention) → Biological (natural enemies) → Chemical (last resort). Reduces pesticide resistance and environmental damage.
  • Indigenous cattle (Gir, Sahiwal): 4-8 L/day, disease-resistant. Exotic (Jersey, Holstein): 20-30 L/day, need high care. Crossbred: 12-16 L/day, balanced.
  • Lactation period: ~280-300 days for dairy cattle. Total yield = Daily yield × Lactation days.
  • Feed Conversion Ratio (FCR) = Feed consumed (kg) ÷ Weight gain (kg). Poultry FCR ~2 (most efficient), Cattle ~7 (least efficient).
  • Poultry: Layers produce 200-300 eggs/year. Broilers reach 1.5 kg in 6-8 weeks. Low FCR, high protein output.
  • Mixed farming: Crops + livestock. Benefits: dung→manure, crop residue→fodder, diversified income, sustainable.
  • Green manuring: Growing legumes (Sunn hemp, Sesbania) and ploughing into soil before flowering. Cheap organic nitrogen source.
  • High Yielding Variety (HYV): Genetically improved through breeding for higher productivity under optimal water, fertilizer, and pest control. Examples: Sonalika wheat, IR-8 rice, Jaya rice.
  • Fish farming (pisciculture): Composite culture combines catla (surface), rohu (middle), mrigal (bottom) in same pond for maximum yield without competition.
  • Common exam topics: Define HYV/IPM (2 marks), Explain crop rotation benefits (3 marks), Compare indigenous vs exotic cattle (3 marks), Calculate yield or milk income (3 marks).

How CBSETUTOR.ai Helps Master Chapter 12

Chapter 12 questions often involve applying concepts to real farming scenarios—calculations, comparisons, and explaining practices. Many students find numericals on yield, NPK, and livestock productivity tricky, and definitions require NCERT-exact language. CBSETUTOR.ai offers a 24×7 AI tutor that lets Class 9 students snap a photo of any Chapter 12 question and receive step-by-step solutions in seconds. Whether it is a numerical on calculating fertilizer quantity, a 5-mark IPM explanation, or a table comparing irrigation methods, the AI tutor breaks down answers in simple language, highlights mark-scoring keywords, and shows worked examples. Parents across Delhi, Mumbai, and Bengaluru appreciate the flat ₹999/month pricing for all subjects and classes 6-12—no per-class upselling. A 3-day free trial lets your child test the platform on Chapter 12 questions before committing. During revision season, students use photo-upload solving to quickly clarify doubts on livestock breed comparisons or NPK ratios without waiting for tuition class next day, helping them stay on track and confident for exams.
  • Upload photo of any Chapter 12 question—numerical, definition, diagram labeling, case study—and get instant, NCERT-aligned solutions.
  • AI tutor explains why an answer is correct, which keywords examiners look for, and common mistakes to avoid in livestock or crop production questions.
  • Access 100+ practice MCQs and assertion-reason questions on Improvement in Food Resources, matching latest CBSE pattern for 2025.
  • Revision tools include flashcards for breed names, nutrient functions, and IPM components—perfect for last-minute memorisation.
  • One subscription (₹999/month) covers all subjects for Classes 6-12. Your Class 9 child can use it for Biology, Maths, and Social Science simultaneously.
  • 3-day free trial with no credit card required. Try it on Chapter 12 doubts this week and decide if it suits your child's learning style.

Frequently asked questions

Are there any actual formulas with variables in CBSE Class 9 Biology Chapter 12?+
No traditional algebraic formulas exist in Chapter 12. However, you use quantitative relationships: Crop yield = Total harvest ÷ Area, Percentage increase = [(New−Old)÷Old]×100, FCR = Feed consumed ÷ Weight gain, and Irrigation efficiency percentage. These are calculation templates tested in 3-mark numericals.
What is the NPK ratio and why is it important for exams?+
NPK ratio shows the proportion of Nitrogen, Phosphorus, and Potassium in fertilizers or required by crops. For example, cereals need 4:2:1 (more N for leaves), root crops need 2:3:2 (more P for roots). CBSE exams ask why a farmer chooses a particular fertilizer or what nutrient deficiency causes specific symptoms. Knowing NPK functions and ratios earns full marks.
How do I remember the difference between manure and fertilizer?+
Manure is organic (comes from animals or plant waste), releases nutrients slowly, improves soil structure, and is bulky. Fertilizer is chemical (manufactured like Urea, DAP), acts fast, nutrient-specific, but does not improve soil texture. NCERT uses these exact terms, so mixing them costs marks. Mnemonic: Manure = More organic, Fertilizer = Fast chemical.
What is the typical milk yield per day for indigenous vs exotic cattle?+
Indigenous breeds (Gir, Sahiwal, Red Sindhi) yield 4–8 litres per day. Exotic breeds (Jersey, Holstein) yield 20–30 litres per day. Crossbred cattle yield 12–16 litres per day. Lactation period is about 280–300 days. CBSE questions often ask to compare breeds or calculate total lactation yield = daily yield × lactation days. Remembering these numbers is crucial for 3-mark questions.
What are the four main irrigation methods and their efficiency percentages?+
1. Flood/Canal irrigation: 40% efficient, cheap but wastes water. 2. Well/Tubewell: 50–60% efficient, common in North India. 3. Sprinkler: 70% efficient, good for uneven land. 4. Drip: 90% efficient, delivers water to roots, ideal for water-scarce regions. CBSE exams ask which method suits a given scenario and why. Always mention efficiency percentage for full marks.
What is Integrated Pest Management (IPM) and what is the correct sequence?+
IPM is a sustainable pest control strategy using multiple methods. Sequence: 1. Cultural (crop rotation, resistant varieties, field sanitation). 2. Biological (natural predators like Trichogramma wasp, ladybird beetle; biopesticides like neem). 3. Chemical (synthetic pesticides only if pest population crosses economic threshold). This minimises chemical use, prevents resistance, and protects environment. CBSE awards marks for correct order and examples.
How is Feed Conversion Ratio (FCR) calculated and why is it important?+
FCR = Total feed consumed (kg) ÷ Live weight gain (kg). Lower FCR means the animal converts feed to body mass efficiently, reducing cost. Poultry FCR is 1.8–2.2 (most efficient), pigs 3–4, cattle 6–8 (least efficient). CBSE questions may ask why poultry is economically better for protein production than cattle—answer using FCR data.
What is crop rotation and what are its benefits?+
Crop rotation is growing different crops sequentially on the same field (e.g., wheat in winter, moong in summer). Benefits: 1. Legumes fix atmospheric nitrogen via Rhizobium bacteria, replenishing soil N. 2. Breaks pest and disease cycles (pests specific to one crop die off). 3. Prevents soil nutrient depletion. 4. Improves soil structure. CBSE often asks for two benefits and one example—mention legume rotation for nitrogen.
What is the difference between intercropping and mixed cropping?+
Intercropping: Growing two or more crops simultaneously in definite row patterns (e.g., maize and soybean in alternate rows). Allows mechanised farming, targeted input application. Mixed cropping: Growing multiple crops together without specific pattern. Common in small farms, reduces risk but harder to manage. Both reduce pest spread and maximise land use, but intercropping is more organised.
What are High Yielding Variety (HYV) seeds and can you give examples?+
HYV seeds are genetically improved crop varieties bred for higher productivity under optimal irrigation, fertilization, and pest control. They played a key role in India's Green Revolution. Examples: Sonalika and Kalyan Sona (wheat), IR-8 and Jaya (rice), Pusa Sawani (okra). CBSE awards marks for naming specific varieties and stating they need good inputs to perform well—writing 'HYV gives more crop' alone is too vague.
How do I calculate percentage increase in crop yield for CBSE exams?+
Formula: Percentage increase = [(New yield − Old yield) ÷ Old yield] × 100. First, calculate yield per hectare = Total harvest ÷ Area for both old and new methods. Then apply the percentage formula. Always write units (quintals per hectare) and show all steps for full marks. For example, if old yield is 10 q/ha and new is 40 q/ha, percentage increase = [(40−10)÷10]×100 = 300%.
What is the role of Rhizobium bacteria in agriculture?+
Rhizobium bacteria live in root nodules of leguminous plants (pulses, beans, peas). They fix atmospheric nitrogen (N₂) into ammonia (NH₃), which plants use for growth. This natural nitrogen fixation reduces the need for chemical nitrogen fertilizers. Farmers practice crop rotation with legumes to replenish soil nitrogen for subsequent cereal crops. CBSE often asks this in 2-3 mark questions—mention nitrogen fixation, legumes, and root nodules.

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