Suppose a school has 20 classes: 16 with 25 students in each, three with 100 students in each, and one with 300 students for a total of 1000 students.
(a) What is the average class size?
(b) Select one of the 1000 students at random and let the random variable X equal the size of that student's class. Define the pmf of X.
(c) What is the mean of X.