In May 1 day, 20 lots (2050-2000)*20= 1000 yuan were closed, and the opening price of 20 lots was 2000 yuan/ton.

On May 2nd, the opening price of 8 lots of long positions was raised to 2040 yuan/ton.

On the closing day of May 3rd, the profit and loss of 28 contracts = (selling price-settlement price of the previous trading day) * contract quantity =(2090-2060)* 28 = 8400 yuan.

Reserve balance =100000+1000+(2090-2000) * 20+(2090-2040) * 8 =103200 yuan.