Three refineries with daily capacities of 6,5 , and 8 million gallons, respectively, supply three distribution areas with daily demands of 4,8 , and 7 million gallons, respectively. Gasoline is transported to the three distribution areas through a network of pipelines. The transportation cost is 10 cents per 1000 gallons per pipeline mile. The following table gives the mileage between the refineries and the distribution areas. Refinery 1 is not connected to distribution area 3 . (a) Construct the associated transportation model using Northwest-corner method, Least-cost method and Vogel approximation method. (b) Determine the optimum shipping schedule in the network