Two-variable functions. The questions are unrelated. (a) Let f(z, y) = r + 2y. Sketch the level curves for the values k = -3, -1, 1,3. Label the level curves. (b) Let g(x, y) = Sketch the domain of g on the ry-plane. (c) Let h(x, y) = yln(x - 3y). Find the partial derivatives h, and hy