A roulette wheel consists of 38 numbers (18 are red, 18 are black, and 2 are green). Assume that with each spin of the wheel, each number is equally likely to appear.
(a) What is the probability of a gambler winning if he bets on a red number showing up?
(b) Suppose the gambler keeps betting on red until he finally wins. Let be the number of times he plays/bets. Specify the probability mass function of the random variable . That is, fin 
(c) Now, suppose the gambler keeps betting on red until he wins twice. Let be the number of times he plays/bets. Specify the probability mass function of the random variable . That is, find 