The time (in minutes) between telephone calls at an insurance claims office has the following exponential probability distribution.

ƒ(x) = .50e –.50xfor x ≥ 0

a. What is the mean time between telephone calls?

b. What is the probability of having 30 seconds or less between telephone calls?

c. What is the probability of having 1 minute or less between telephone calls?

d. What is the probability of having 5 or more minutes without a telephone call?