ANSWER B! NEED TO SHOW WORKING

The Fast Shop Drive-In Market has one checkout counter where one employee operates the cash register. The combination of the cash register and the operator is the server in this queuing system; the customers who line up at the counter to pay for their selections form the waiting line. Customers arrive at a rate of one every 3 minutes according to a Poisson distribution, and service times are exponentially distributed, with a mean rate of 30 customers per hour.

B) Because of the nature of the store, customers purchase a few items and expect quick service. Given customers expectations, the manager believes that the waiting time is unacceptable. The manager wants to test two alternatives for reducing customer waiting time: I) adding extra employees to pack up the purchases (and hence increasing the service rate), II) adding more checkout counters with all the counters served by the same line. With the help of the markets national offices marketing research group, the manager has determined that each customer waiting cost in the system is $70 per week to the store. The regular salary of the cashier is $180/week. Alternative I: Adding extra employee Adding extra employees will cost the market manager $100 per week for each employee added (since these extra employees will not be cashiers but only packers, so the rate is less). However, each extra employee will increase the service rate by 10 customers per hour. Note that there will be a single cash counter.