Question $2(3$ points $1$ point per part$)$

Benny the Barber $($see Question $1)$ is considering the addition of a second chair. Customers would be

selected for a haircut on a FCFS basis from those waiting. Benny has assumed that both barbers would

take an average of $20$ minutes to give a haircut, and that business would remain unchanged with

customers arriving at a rate of two per hour. Find the following information

to help Benny decide if a second chair should be added:

Part $($a$)$: The average number of customers waiting.

Part $($b$)$: The average time a customer waits.

Part $($c$)$: The average time a customer is in the shop.