A quality inspector selects a sample of 12 items at random from a collection of 60 items, of which 18 have excellent quality, 25 have good quality. 12 have poor quality, and 5 are defective.
(a) What is the probability that the sample only contains items that have either excellent or good quality?
(b) What is the probability that the sample contains three items of excellent quality, three items of good quality, three items of poor quality, and three defective items?