a) Find and classify the critical points of f(x,y) = 3r - 2xy + 2y - 10x + 1 by means of one of the methods introduced in the course. (1 p) b) Calculate the absolute maximum and minimum values of f(x,y) = y-y-x-5 on the square 0x 1 and 0 y 1. (1 p) c) Determine the extreme values of the function f(x,y,z) = 12x + yz subject to the constraints x-z = 0 and y + 2 = 36 by means of Lagrange multipliers. (2 p)