Chapter 3.2, Problem 22E

Refer to Exercise 13, and calculate and graph the cdf F(x). Then use it to calculate the probabilities of the events given in parts (a)-(d) of that problem.

13. A mail-order computer business has six 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.

x	0	1	2	3	4	5	6
p(x)	.10	.15	.20	25	.20	.06	.04

Calculate the probability of each of the following events.

1. a. {at most three lines are in use}
2. b. {fewer than three lines are in use}
3. c. {at least three lines are in use}
4. d. {between two and five lines, inclusive, are in use}
5. e. {between two and four lines, inclusive, are not in use}
6. f. {at least four lines are not in use}