In Exercises 40 through 49, assume that the required extreme value is a relative extremum.

In relation to a rectangular map grid, four oil rigs are located at the points (−300, 0), (−100, 500), (0, 0), and (400, 300) where units are in feet. Where should a maintenance shed M(a, b) be located to minimize the sum of squares of the distances from the rigs?