Bloomington has two hospitals. Hospital 1 has four ambulances, and hospital 2 has two ambulances.

Ambulance service is deemed adequate if there is only a 10% chance that no ambulance will be available when an ambulance call is received by a hospital. The average length of an ambulance service call is 20 minutes.

Given this information, queueing theory tells us that hospital 1 can be assigned up to 4.9 calls per hour and that hospital 2 can be assigned up to 1.5 calls per hour. Bloomington has been divided into 12 districts.

The average number of calls per hour emanating from each district is given in the file P05_71.xlsx. This file also shows the travel time (in minutes) needed to get from each district to each hospital. The objective is to minimize the average travel time needed to respond to a call. Determine the proper assignment of districts to hospitals. (Hint: Be careful about defining the supply points!)