The NPR show Wait Wait ... Don’t Tell Me gives its guests a three-question quiz in which they have three answer choices for each question. The questions are so obscure that the guest typically must just randomly guess at the answers. Let’s suppose it is always true that a guest must randomly guess which of the three answers correctly. 

a. Create a probability distribution where X is the number of questions (out of three) the guest answers correctly. 

b. To win the game, someone must answer at least two out of three questions correctly. What is the probability someone wins if he or she is just guessing?