A certain gym teacher has a class of 20 students. He wants to divide them into four teams of five students each in order to have a class basketball tournament.

(a) How many different ways can he divide the class into four teams?

(b) Tommy and Bobby are two of the students in the class and are best friends. Assuming the gym teacher assigns students in a completely random fashion, what is the probability that they get selected to be on the same team?

(c) Neither boy wants to be on a team with the class bully, Frank. What is the probability that neither Tommy nor Bobby are on the same team as Frank?