Question 1: On April1day, I bought 40 lots of mung bean futures contracts (each lot 10 ton) and sold 20 closed mung bean futures contracts with a transaction price of 3030/ ton and a closing profit of 20 *10 * (30. The profit of long positions is 20* 10*(3040-3000)=8000 yuan. Customer's profit of the day 14000 yuan. The position margin is 20* 10*3040*5%=30400.

Question 2: On April 2, the customer bought another 8 lots of mung bean contracts, with a transaction price of 3030/ ton and a settlement price of 3060/ ton that day. The profit of holding 20 lots is 20* 10*(3060-3040)=4000 yuan, and the profit of new positions is 8 * 10 * (3000).

Account settlement reserve balance: (10000+14000+4000+2400)-42840 = 77560.

Question 3: On April 3, the customer closed 28 lots of mung bean contracts, and the transaction price was 3070/ ton. Profit from liquidation: 28* 10*(3070-3060)=2800, and the short position margin is zero.

At this time, the balance of reserve fund for account settlement is: (10000+14000+4000+2400)+2800 =123200.