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3. For the function P(x, y) = 6x - 6x y' + y' + 3y', (a) find all critical points and classify them as local minima, local maxima, or saddle points (2.5 pts); (b) use the method of Lagrange multipliers to find the absolute maximum and minimum of P(x, y) on the circle x3 + y = 4 (i.e., subject to the constraint x- + y- = 4) (2 pts) (c) combine your answers to (a) and (b) to find the absolute maximum and minimum of P(x, y) on the region x'+ y'