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 hours to win 3 times.
b) How many minutes do you expect to need to win 3 times?