A, B and C are three friends who often like to compete with one another.

(a) they are equally skillful in playing table tennis. A plays B first while C waits. the winner then plays C while the loser waits. This method of play goes on until one of them wins two consecutive sets. this person then gets a prize. find the probability that C gets the prize. ( ans: 2/7)

(b) they are given the same multiple-choice quiz to answer independently. the quiz has 10 questions, each provided with 4 possible answers. only one of which is correct. A knows eight of the correct answers, B knows seven, and C knows six. All of them then answer the remaining questions by sheer guess. No penalty is imposed on a wrong answer. What is the probability that C beats A and B?

(ans: 0.0259)

I can't figure out the method of solving this problem even after looking at the answers. Can someone help?