Twenty-three subjects volunteer for a study of a new cold medicine. Ten of the volunteers are ages 20-39, 6 are ages 40-59, and 7 are age 60 or older. If 9 volunteers are selected at random, find the following probabilities. (a) the probability that all the volunteers selected are ages 20-39 (b) the probability that 5 of the volunteers are ages 20-39 and 4 are age 60 or older (c) the probability that 4 of the volunteers are ages 40-59