The owner is working out his staffing needs. The restaurant will be open in the evenings from 5 pm to 9 pm. He anticipates different number of servers required during each of the 4 hours depending on the anticipated demand. These requirements are presented in the figure below. Servers have to be scheduled in 2 hour work shifts. There are 5 possible shifts: 5 pm - 7 pm, 5:30 pm - 7:30 pm, 6 pm - 8 pm, 6:30 pm - 8:30 pm, and 7 pm - 9 pm. Mr. Ranatunga would like to minimize the number of server-shifts scheduled each evening while ensuring that the capacity requirements are met. Write down an integer linear program to solve this problem for Mr. Ranatunga. Clearly mention what your decision variables mean.