At a certain restaurant, during the working day, there are 12 customers. Seven of them have pizza, and the other five have burgers. Suppose that a person is conducting a survey of three customers at the restaurant, and he conducts the survey without replacement, i.e., he does not talk to the same customer more than once. All possible selections of three people for the survey are equally likely.
Let X be the number of people in the survey who are eating pizza.
a. What is the mass of X?
b. Evaluate the mass at the four values where the mass is strictly positive.
Make sure that your four numbers sum to 1.)
c. What is the average number of people in the survey who are eating pizza?