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EXCEL SOLUTION OF TRANSPORTATION, ASSIGNMENT AND TRANSSHIPMENT PROBLEMS  339


                                      Solver are the decision variables, the objective function, the constraint left-hand
                                      sides and the constraint right-hand sides. These cells are screened in the bottom
                                      portion of the worksheet.
                                         Decision Variables  Cells B17:E19 are reserved for the decision variables. The
                                                           optimal values are shown to be x 11 ¼ 3500, x 12 ¼ 1500,
                                                           x 22 ¼ 2500, x 23 ¼ 2000, x 24 ¼ 1500 and x 41 ¼ 2500. All
                                                           other decision variables equal zero indicating nothing will
                                                           be shipped over the corresponding routes.
                                         Objective Function  The formula ¼ SUMPRODUCT(B5:E7,B17:E19) has been
                                                           placed into cell C13 to compute the cost of the solution. The
                                                           minimum cost solution is shown to have a value of E39 500.
                                         Left-Hand Sides   Cells F17:F19 contain the left-hand sides for the supply
                                                           constraints, and cells B20:E20 contain the left-hand sides
                                                           for the demand constraints.
                                                             Cell F17 ¼ SUM(B17:E17)   (Copy to F18:F19)
                                                             Cell B20 ¼ SUM(B17:B19)   (Copy to C20:E20)
                                         Right-Hand Sides  Cells H17:H19 contain the right-hand sides for the supply
                                                           constraints, and cells B22:E22 contain the right-hand sides
                                                           for the demand constraints.
                                                             Cell H17 ¼ F5  (Copy to H18:H19)
                                                             Cell B22 ¼ B8  (Copy to C22:E22)

                                      Excel Solution
                                      The solution shown in Figure 7.14 can be obtained by selecting Solver from the
                                      Tools menu, entering the proper values into the Solver Parameters dialogue box,
                                      selecting Standard Simplex LP and specifying the option Assume Non-Negative.
                                      Then click Solve. The information entered into the Solver Parameters dialogue box
                                      is shown in Figure 7.15.

                                      Assignment Problem
                                      The first step is to enter the data for the assignment costs in the top portion of the
                                      worksheet. Even though the assignment model is a special case of the transportation
                                      model, it is not necessary to enter values for origin supplies and destination demands
                                      because they are always equal to one.


                                      Figure 7.15 Solver Parameters Dialogue Box for the Foster Electronics Problem


























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