PREP PS1里的一道题，不会做，也找不到讨论

58.   7090-!-item-!-187;#058&005463

In the graduating class of a certain college, 48 percent of the students are male and 52 percent are female.  In this class 40 percent of the male and 20 percent of the female students are 25 years old or older.  If one student in the graduating class is randomly selected, approximately what is the probability that he or she will be less than 25 years old?

(A) 0.90

(B) 0.70

(C) 0.45

(D) 0.30

The answer is B.

0.48*0.6+0.52*0.8=0.704

做了一下，B。和2楼方法一样