Suppose that 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 a student randomly out of the 1000 students. Let the random variable X equal the size of the class to which this student belongs and define the p.m.f. of X
c) Find the mean of X.