(5) Find the equations and sketch the graphs of at least 4 different level curves for the surface f(x,y) = xy. Include in your sketch the level curves z=-1, z=0, z=1, z=2. (Hint: you need to use Quadrants I and III for z = 1 and Quadrants II and IV for z = -1.) Sketch these on the same graph, so that your illustration starts to look like a topographic map. Which direction will rainwater flow if it lands at the point on the surface corresponding to (x, y) = (1,1)? Which direction(s) will rainwater flow if it lands at the point on the surface corresponding to (x, y) = (0, 0)?