20% margin and 50% capital utilization mean that the actual margin ratio is 20%*( 1/50%)=40%, and the leverage ratio is 1/40%=2.5. (Only 1 yuan can be used in 2 yuan, but the purchasing power of this 1 yuan is equivalent to that of 5 yuan when buying the contract, so the purchasing power of each 1 yuan on the books is equivalent to that of 2.5 yuan, and the leverage ratio is 2.5).

From 10000 to 30000, the contracted cotton output is 200%. The actual rate of return (no floating profit plus positions) is 2.5*200%=500%. Assuming that there are n floating profits and positions in the period, the ending book capital = 4000 * (1+500%/n) N. If n is infinite, the ending book capital = 4000 * e (5) = 595531.1894528 yuan.

The key to this calculation is to allow non-integer positions. Practically speaking, the money is not enough to open a position. .