Suppose that (x, y) = x xy + y 2x + 2y with D = {(x, y) | 0 y x 2}. 1. The critical point of f(x, y) restricted to the boundary of D, not at a corner point, is at (a, b). Then 1 3 and b = 2. Absolute minimum of f(x, y) is and the absolute maximum is a = X