The television game show The Price Is Right has a game called the Shell Game. The game has four shells, and one of these four shells has a ball under it. The contestant chooses one shell. If this shell contains the ball, the contestant wins. If a contestant chooses one shell randomly, what is the probability of each of the following outcomes?
a. Contestant wins
b. Contestant loses
Do these probabilities add up to 1.0? If yes, why?