Lenny, a Graduate Research Assistant, "Moonlights" at the Short Order

Short Answer

Lenny, a graduate research assistant, "moonlights" at the short order counter in the student union snack bar in the evenings. He is the only one on duty at the counter during the hours he works. Arrivals to the counter seem to follow the Poisson distribution with a mean of 8 per hour. Each customer is served one at a time and the service time follows an exponential distribution with a mean of 5 minutes.
-How long will a student wait in line, on average?