摘要：
When Mr. and Mrs. Clinton's twin sons Ben and Bill had their tenth birthday, the party was held at the McDonald's restaurant at South Broadway 202, Ne... 阅读全文
摘要：
N friends go to the local super market together. The probability of their buying something from themarket is p1, p2, p3, . . . , pN respectively. Afte... 阅读全文