问题如下：
Use a two-step tree to value an eight-month American put option on a futures contract. The current futures price is 58 and the risk-free rate is 5%. The strike price is 60 and the volatility is 24% per annum.
选项：
解释：
The option is exercised at node A. The value today is 5.478.
老师，请问这里的时间为什么是4/12，而不是8/12？
