題組內容

2. (20%) An urn contains five balls, one marked $W$ and four marked $L$. You and another player take turns selecting a ball at random from the urn, one at a time. The first person to select $W$ ball is the winner.

(c) (5%) If balls are selected with replacement. Let \( X \) denote the number of selected balls if you are the winner. Find the probability mass function.