The National Bank of Warwick is concerned with complaints from customers about its drive-through window operation. Customers complain that it sometimes takes too long to be served and since there are often cars in front and back of a customer, they cannot leave if the service is taking a long time. To correct this problem the bank installed an intercom system so the drive-through window teller can call for assistance if the line backs up or a customer has an unusually long transaction. The bank”s objective is an average custome”s waiting and service time of approximately 3 minutes. The bank”s operations manager wants to monitor the new drive-through window system with SPC. The manager has timed five customers” waiting and service times at random for 12 days as follows:

Develop an -chart to be used in conjunction with an R-chart to monitor this drive-through window process and indicate if the process is in control using these charts.