In an article published in the European Journal of Operutiontrl Research (Vol. 21, 1985) the vehicle-dispatching decisions of an airport-based taxi service were investigated. In modeling the system, the authors assumed travel times of successive trips to be independent exponential random variables. Assume A = ,051.

a. What is the mean trip time for the taxi service'?

b. What is the probability that a particular trip will take more than 30 minutes'?

c. Two taxis have just been dispatched. What is the probability that both will be gone for more than 30 mjnutes? That at lcast one of the taxis will return within 30 minutes?