A large drug company must determine how many sales representatives to assign to each of four sales districts. The cost of having R representatives in a district is ($88,000 + $80,000R) per year. If a "rep" is based in a given district, the average time (in hours) required to complete a call on a doctor in each of the four districts is given in the table below. District of Call District of Rep 1 2 3 0.9 4.1 5.4 6.8 N 3.3 1.7 2.6 5.3 4.5 3.0 1.4 1.9 A 6.5 5.3 2.4 1.3 Each sales rep can work up to 160 hours per month, and the required number of monthly calls for each district are: District # of Calls 150 NH 240 300 180 Provide a complete formulation for the problem. Make sure to clearly define the variables, objective, and all constraints. Constants used for fixed charge constraints, if any, should be set at their minimum "safe" values