You are a contestant on a TV game show with five doors. There is just one prize behind one door, randomly selected. After you choose, the hosts deliberately open three doors (other than your choice) that do not have the prize. You have the opportunity to switch doors from your original choice to the other unopened door. 

a. What is the probability of getting the prize if you switch? 

b. What is the probability of getting the prize if you do not switch?