Fifteen telephones have just been received at an authorized service center. Five of these telephones are cellular, five are cordless, and the other five are corded phones. Suppose that these components are randomly allocated the numbers 1, 2, ……15 to establish the order in which they will be serviced.
a. What is the probability that all the cordless phones are among the first ten to be serviced?
b. What is the probability that after servicing ten of these phones, phones of only two of the three types remain to be serviced?
c. What is the probability that two phones of each type are among the first six serviced?
