问题如下：
Suppose the probability of a good economy is 0.4 and the probability of a poor economy is 0.6. The conditional probabilities of product H's profit are in the table below. What is the expected profit of product H?
选项：
A.15.
B.10.2.
C.12.5.
解释：
B is correct
E(H)=E(H|Good)+E(H|Poor)
E(H|Good) = 0.1*0+0.3*10+0.6*20=15, and E(H|Poor) = 0.5*0+0.3*10+0.2*20 = 7,
E(H) = (0.4)(15) + (0.6)(7) = 10.2.
请问可不可以直接0.4*0.3*10+0.4*0.6*20+0.6*0.3*10+0.6*0.2*20？0.4*0.3是直接算出经济好时候赚10这个最终情境的概率，没有像答案里那样分步，不知道对不对
