Arrow Coffee Shop (Q13)

(Q13)Arrow Coffee is a small coffee shop in Marylebone. It has on average 3 people waiting in the queue and the average wait at the counter before being served is two minutes. The coffee shop has two people behind the counter taking orders and they are busy 75 percent of the time.

The coffee shop wants to place an upper specification limit of 40 seconds on the service time, i.e., the time an employee spends taking a customer order. Do you think this is a reasonable specification limit to set? State your assumptions and show your calculations.