A roulette wheel has 38 slots – 18 red, 19 black, and 2 green (the house wins on green). Suppose the spins of the wheel are independent and that the wheel is fair. The wheel is spun twice.

a. What is the probability that both spins are green if we know that at least one spin is green.？

b. Suppose that we win 10$ if the spin is red and lose 10$ if the spin is not red(black or green). Let X denote the amount won ate the end of two spins. Find the probability function of X, p(x)=P[X=x]