a) (9 pts) The temperature at a point (x, y z) on the surface + =3 is given by 1 T ( x, y , z ) =- -. Find the highest and lowest temperature on the surface. X Z b) (9 points) Use a suitable change of variable to evaluate the integral edA where D D is the region in the first quadrant of the xy-plane lying between the curves: xy = 1, xy = 2, x2y = 1 and x2y = 4