9. A mail-order computer business has five telephone lines. Let X denote the number of lines in use at a specified time. Suppose the pmf of X is as given in the accompanying table. 0 1 2 3 4 5 p(x) .10 .15 .20 -25 22.08 2 Calculate the probability of each of the following events: [4] a. at most 3 lines are in use [4] b. fewer than 3 lines are in use [4] c. at least 3 lines are in use [4 d. between 2 and 5 lines, inclusive, are in use