You are planning the new layout for the local branch of the Sixth Ninth Bank. You are considering separate cashier windows for the three different classes of service. Each class of service would be separate with its own cashiers and customers. Oddly enough, each class of service, while different, has exactly the same demand and service times. People for one class of service arrive every four minutes and arrival times are exponentially distributed (the standard deviation is equal to the mean). It takes seven minutes to service each customer, and the standard deviation of the service times is three minutes. You assign two cashiers to each type of service.

a. On average, how long will each line be at each of the cashier windows?

b. On average how long will a customer spend in the bank (assume they enter, go directly to one line, and leave as soon as service is complete). You decide to consolidate all the cashiers so they can handle all types of customers without increasing the service times.

c. What will happen to the amount of time each cashier spends idle? (increase, decrease, stay the same, depend on ________ )

d. What will happen to the average amount of time a customer spends in the bank? (increase, decrease, stay the same, depend on ________ )