You didn't give the tonnage of each hand. Dalian soybean per lot 10 ton. According to your algorithm, it should be 5 tons per hand.

This question is based on your 5 tons/lot, regardless of the handling fee.

Your understanding of margin occupation is wrong. The figure you calculated should be multiplied by the margin ratio (5%), which should actually be 14420.

The first day of customer rights and interests: 20 * 50 * 5+20 * 40 * 5+100000 =109000;

Customer's rights and interests of the next day:109000+28 * 20 * 5 =11800.

Risk14420/111800 =12.9%

I don't know how your answer came from. The conditions may be different ~