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3. Suppose that two teams are playing a series of games, each of which is independently won by team A with probability p and by team B with probability 1 - p. The winner of the series is the first team to win four games. Let X be the number of games that are played. a. Derive the distribution of X. b. Find the expected value of X. c. Evaluate your answer to part a. when p = 1/2