1,无风险报酬率只是用来对行权价格折现，是一种机会成本

期权的现金流无法预测，所以无所谓风险资产要求的收益率

Delta:H/(X+H-P2), where P2 is the stock price under X

Amount borrowed:H*(X+H)/(X+H-P2)/(1+r),where r is the annual interest rate

Value of Call: X*H/(X+H-P2)-H*(X+H)/(X+H-P2)/(1+r)