Consider the function h(x, y) = xy x 2 + y 2 . a) Use polar coordinates to show that the range of f is [ 1 2 , 1 2 ]. b) Find equations for the level curves for c = 1 2 , 1 4 , 0, 1 4 , 1 2 . c) Sketch a contour plot for h. (Keep in mind that (0,0) is not in the domain of h.) d) How does the contour plot show that lim (x,y)(0,0) h(x, y) does not exist?