Location Problem with Two Sites. Oliveira Office Supply has a large retail system consisting of twelve stores spread around the country, often in direct competition with Kilroy. However, managers at Oliveira have decided to use two national distribution centers. When Oliveira's stores are mapped on the same grid as Kilroy's, the store locations occur at the coordinates listed in the following table. As in the previous exercise, there are also data to indicate how many trips are made annually to each store: Coordinates Trips Site (k) xk yk nk 1 2 96 21 2 5 41 12 3 20 10 20 4 44 48 15 5 60 58 27 6 100 4 8 7 122 94 21 8 138 80 16 9 150 40 10 10 170 18 18 11 182 2 25 12 190 56 14 Find the optimal location for Oliveira's two distribution centers in this expanded version of the problem. What is the optimal value of the objective function?

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