"An airport ground operations firm seeks to minimize the cost of human resource for its passenger services. The airport runs 7/24 and the number of passengers fluctuates with the time of the day. To maintain the quality of the service, the operations manager keeps the passengers-to-service personnel ratio at a threshold level. Hence the number of personnel needed has to be optimized as the number of passengers change. The personnel works eight successive hours a day only with five-shift schedule starting at 4 a.m., 8 a.m., 12 p.m., 4 p.m. and 8 p.m."

The problem given above is an example of which of the following?