A company has three manufacturing plants (in Atlanta, Tulsa, and Springfield) that produce a product that is then shipped to one of four distribution centers - A, B, C, or D. The three plants can produce 15, 22, and 15 truckloads of product each week, respectively. Distribution centers A & B need 12 truckloads of product each week and Distribution centers C & D need 13 truckloads of product each week. The shipping costs per truckload between the plants and distribution centers are given in the table. The company needs to determine how much to ship from each plant to each distribution center, and would like to minimize total shipping costs. Distribution Center Plant A B C D Atlanta $ 800 $1300 $400 $ 700 Tulsa $1100 $1400 $600 $1000 Springfield $ 600 $1200 $800 $ 900 a. What are the objective function, decision variables, and constraints for this optimization problem? b. Develop an Excel spreadsheet and use Excel-Solver to find an optimal solution for this problem. c. Describe the optimal solution in words