Referring to the previous problem, suppose that Allied Freight can purchase and ship extra units to either warehouse for a total cost of $100 per unit and that all customer demand must be met. Determine how to minimize the sum of purchasing and shipping costs.

Data from Previous Problem:

Allied Freight supplies goods to three customers, who each require 30 units. The company has two ware-houses. In warehouse 1, 40 units are available, and in warehouse 2, 30 units are available. The costs of shipping one unit from each warehouse to each customer are shown in the file P05_67.xlsx. There is a penalty for each unsatisfied customer unit of demand—with customer 1, a penalty cost of $90 is incurred; with customer 2, $80; and with customer 3, $110.