A personnel manager must schedule the police force in such a way as to satisfy the staffing requirements shown in the table below TIME Minimum number of officers required Midnight-4 A.M. 5 4 A.M.-8 A.M. 7 8 A.M.- Noon 15 Noon-4 P.M. 7 4 P.M.-8 P.M. 12 8 P.M.-Midnight 9 Shift Starting Time Ending Time 1 Midnight 8:00 A.M. 2 4:00 A.M. Noon 3 8:00 A.M. 4:00 P.M. 4 Noon 8:00 P.M. 5 4:00 P.M. Midnight 6 8:00 P.M. 4:00 A.M. The officers work 8-hour shifts. There are 6 such shifts each day. The starting and ending times for each shift are given in the table above. The personnel manager wants to determine how many officers should work each shift in order to minimize the total number of officers employed, while still satisfying the staffing requirements. Formulate the problem as an integer linear programming model