You vow to replay a tough level in Super Mario World until you win 3 times. Assume that you have a 25% chance of winning each time you play, and each round is independent (your skill does not improve from game to game, because there is a lot of luck involved). Let X denote the number of times you have to play. Each attempt takes 5 minutes.
a. What is the probability it will take you more than an hour to win 3 times?
b. How many minutes do you expect to need to win 3 times?