1. The profits from Jiwei shrimp farming are very considerable. About 120 kilograms of seed shrimp are put into each mu. With each ring's rolling breeding and rearing method, the annual output per mu can reach about 3,000 kilograms. The shrimp seeds are put in at one time. No more seeds will be purchased and put in for 3-5 years, and the offspring generations will not degrade. There is no variation, and the yield per mu remains unchanged for a long time.

2. Based on the base estimate of 120 kilograms of broiled shrimp per mu, the number of female shrimps per mu is: 120 kilograms/mu , 1140/mu 30%, calculated based on the minimum 8%, the total number of annual adult shrimps is: 456,000/year × 8% = 36,480/mu/year. The eggs can be put on the market after 2-3 months. The weight of each adult shrimp grows to 50 grams (about 10 animals/jin), the total annual output per mu is: 36480 animals/mu·year÷12 animals/jin=3040 catties/mu/year, then the annual gross profit per mu is: 3040 catties×8 yuan/ Jin = 24,320 yuan/mu

4. Net profit = gross profit 24,320 yuan - seed purchase cost (120 jin × 48 yuan) 5,760 yuan = 18,560 yuan/mu.