Given the relation x +xy + 3xyz + 5y'z -2z"= 0, assume that & is defined as a function of x andy. Find 23 and DZ as expressions in x, y, and z. (8 points ) Ox dy Find the critical points of f (x,y) = x3 - 3xy + y - 2x + 5x. Calculate D(x, y) and classify those points. ( 10 pts.)