From "Matching Supply with Demand" - Cachon/Terwiesch - Chapter 2- Q2.2
Consider the baggage check-in of a small airline. Check in data indicate that from 9am to 10am, 255 passengers checked in. Moreover, based on counting the number of passengers waiting in line, airport management found that the average number of passengers waiting for check-in was 35. How long did the average passenger have to wait in line?