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340   CHAPTER 7 TRANSPORTATION, ASSIGNMENT AND TRANSSHIPMENT PROBLEMS


                                       The linear programming model is developed in the bottom portion of the
                                     worksheet. As with all linear programmes the model has four key elements:
                                     the decision variables, the objective function, the constraint left-hand sides and
                                     the constraint right-hand sides. For an assignment problem the decision variables
                                     indicate whetherapersonisassignedtoatask (witha1for yesor0 forno);the
                                     objective function is the total cost of all assignments; the constraint left-
                                     hand sides are the number of tasks that are assigned to each person and the
                                     number of people that are assigned to each task; and the right-hand sides are
                                     the number of tasks each person can handle (1) and the number of people each
                                     task requires (1).
                                       The worksheet formulation and solution for the Fowle Marketing Research
                                     Problem (see Section 7.3) are shown in Figure 7.16.


                                     Formulation
                                     The data and descriptive labels are contained in cells A1:D7. Note that we have not
                                     inserted supply and demand values because they are always equal to 1 in an assign-
                                     ment problem. The model appears in the bottom portion of the worksheet with the
                                     key elements screened.
                                       Decision Variables  Cells B16:D18 are reserved for the decision variables. The
                                                         optimal values are shown to be x 12 ¼ 1, x 23 ¼ 1, and x 31 ¼ 1
                                                         with all other variables ¼ 0.
                                       Objective Function  The formula ¼SUMPRODUCT(B5:D7,B16:D18) has been
                                                         placed into cell C12 to compute the number of days
                                                         required to complete all the jobs. The minimum time
                                                         solution has a value of 26 days.




                                     Figure 7.16 Excel Solution Of The Fowle Marketing Research Problem












                     EXCEL file
                         FOWLE






















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