In Exercises 29 through 35, assume that the required extreme value is a relative extremum.

A company produces x units of commodity A and y units of commodity B. All the units can be sold for p = 100 − x dollars per unit of A and q = 100 − y dollars per unit of B. The cost (in dollars) of producing these units is given by the joint-cost function C(x, y) = x² + xy + y². What should x and y be to maximize profit?