A small convenience store normally has one employee attending to the cash register. The average time between customer arrivals at the store is 5 minutes. The average service time at the cash register is 3 minutes. What percentage of the time will the cashier be busy in serving customers?
A small convenience store normally has one employee attending to the cash register. The average customer arrival rate is 90 customers per hour. The cashier, when fully busy, can serve 60 customers per hour. If the store could provide two cashiers at the counter with two cash registers, the average wait time for customers before they can start being served by a cashier is expected to be ______