6.2.* Consider the transportation problem having the unit shipping costs shown in the following table. 6 F Destination 1 2 3 Supply Source 1 40 6 5 7 8 4 6 2 60 Demand 30 40 30 a. Formulate a network model for this problem as a minimum-cost flow problem by drawing a network similar to Figure 6.3. b. Formulate and solve a spreadsheet model for this problem. [80] [-60] $700 F1 W1 $300 $200 [50] [0]. DC $400 [50] $500 [50] $1,000 F2 W2 [70] [-90] FIGURE 6.3 A network model for the Distribution Unlimited Co. problem as a minimum-cost flow