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 actually appeared in 8 of them.
a. How many ways are there to select a sample of 5 buses from the 25 for a thorough inspection?
b. In how many ways can a sample of 5 buses con- tain 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 will have visible cracks?
d. If buses are selected as in part (c), what is the probability that at least 4 of those selected will have visible cracks?