3. Shortly after being put into service, some buses manufactured by a certain company have developed cracks on the underside of the main frame. Suppose a particular city has 25 of these buses and cracks have appeared in 8 of them. [Think to yourself that this is similar to a 52-card deck with 13 hearts.]

a) How many ways can you select a sample of 5 buses from the 25 to inspect?

b) In how many ways can a sample of 5 buses contain exactly 4 with visible cracks?

c) If a sample of 5 buses is chosen at random, what is the probability that exactly 4 of the 5 buses will have visible cracks?

d) If a sample of 5 buses is chosen at random, what is the probability that at least 4 of the 5 buses will have visible cracks?