NO.PZ2017092702000095
问题如下：
A call option on a stock index is valued using a three-step binomial tree with an up move that equals 1.05 and a down move that equals 0.95. The current level of the index is $190, and the option exercise price is $200. If the option value is positive when the stock price exceeds the exercise price at expiration and $0 otherwise, the number of terminal nodes with a positive payoff is:
选项：
A.one.
B.two.
C.three.
解释：
A is correct.
Only the top node value of $219.9488 exceeds $200
题目中哪里确定的是 两层，即 先按照1.05 和0.95 先得到一层，然后再根据当前值 *1.05 得到了第三层的数据，就是怎么看出来第三层是terminal数据。
