Customers exhibit a Poisson arrival distribution and the barber must provide an exponential service distribution. Market data indicates that customers arrive at a rate of 2 per hour. It will 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:
a. The average number of customers waiting.
b. The average time a customer waits.
c. The average time a customer is in the shop.