=6.11. The Texago Corporation has four oil fields, four refineries, and four distribution centers in the locations identified in the next tables. A major strike involving the transportation industries now has sharply curtailed Texago’s capacity to ship oil from the four oil fields to the four refineries and to ship petroleum products from the refineries to the distribution centers. Using units of thousands of barrels of crude oil (and its equivalent in refined products), the following tables show the maximum number of units that can be shipped per day from each oil field to each refinery and from each refinery to each distribution center. The Texago management now wants to determine a plan for how many units to ship from each oil field to each refinery and from each refinery to each distribution center that will maximize the total number of units reaching the distribution centers.