The district manager of a fast-food restaurant chain was receiving numerous complaints about customers waiting too long at the counter to place and receive their order. During the peak hour of store operation, the district manager’s audit team found that customers arrived at an average rate of one customer every minute. The standard firm service time was 2.5 minutes per customer. The store had three cash registers (service channels) open during this audit time but four were available (i.e., one was idle). The fourth cash register was not opened because the store manager did not schedule an extra employee to work that day. Use the Multiple Server Queue Excel template to answer the following questions:

a. What is the probability that the system is empty?

b. What is the probability that a customer must wait for service?  

c. What is the average number of customers waiting for service in the queue?

d. What is the average wait time in the queue?  0.059*60 = 3.54 minutes

e. How would opening the fourth cash register have impacted service?