Problem 4-09 Epsilon Airlines services predominately the eastern and southeastern United States. A vast majority of Epsilon's customers make reservations through Epsilon's website, but a small percentage of customers make reservations via phone. Epsilon employs call-center personnel to handle these reservations along with any problems with the website reservation system and for the rebooking of flights for customers if their plans change or their travel is disrupted. Staffing the call center appropriately is a challenge for Epsilon's management team. Having too many employees on hand is a waste of money, but having too few results in very poor customer service and the potential loss of customers. Epsilon analysts have estimated the minimum number of call-center employees needed by day of week for the upcoming vacation season (June, July, and the first two weeks of August). These estimates are as follows: Day Minimum Number of Employees Needed 75 50 45 Monday Tuesday Wednesday Thursday Friday Saturday Sunday 60 90 75 45 The call-center employees work five consecutive days and then have two consecutive days off. An employee may start work any day of the week. Each call-center employee receives the same salary. Assume that the schedule cycles and ignore start-up and stopping of the schedule. Develop a model that will minimize the total number of call-center employees needed to meet the minimum requirements. Find the optimal solution. Give the number of call-center employees that exceed the minimum required. Use a software package LINGO or Excel Solver. If your answer is zero, enter "O". Let Xi = the number of call center employees who start work on day i (i = 1 = Monday, i = 2 = Tuesday...) Min X1 X2 X3 X4 X5 X6 X7 s.t. X1 X2 X3 X4 X5 X7 X1 X2 X2 X2 X5 X6 X7 X1 X2 X3 X4 X5 X6 X7 X1 X2 X3 X4 X5 X6 X7 X1 X2 X3 X4 X5 X6 X7 X1 X2 X3 X4 X5 X6 X7 + X1 X2 X3 X4 X5 X6 X7 X1, X2, X3, X4, X5, X6, X7 > 0 Solution: X1 X2 X3 = X4 X5 X6 X7 Number of excess employees: Monday Tuesday Wednesday = Thursday Friday Saturday Sunday Total Number of Employees