The Emergency-Facilities Location Problem

Background:

The township of Rio Rancho has hitherto not had its own emergency facilities. It has secured funds to erect two emergency facilities in 1986, each of which will combine ambulance, fire, and police services. Figure 1 indicates the demand, or number of emergencies per square block, for 1985. The "L" region in the north is an obstacle, while the rectangle in the south is a part with a shallow pond. It takes an emergency vehicle an average of 15 seconds to go one block in the N-S direction and 20 seconds in the E-W direction. Your task it to locate the two facilities so as to minimize the total response time.