24. The probability mass function of X is given by p(k) =

r + k − 1 r − 1



pr(1 − p)

k , k = 0, 1,...

Give a possible interpretation of the random variable X.

Hint: See Exercise 23.

In Exercises 25 and 26, 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 i games.