f) Determine whether the space curve given by r(t) = (t, ts, t2 + 1) intersects the xy- plane, and if does, determine where. g) Describe the level surfaces of the function f(x, y, z) = \\x2 + y2 + z2. h) Determine all values of the constant a such that the function f(x, y) = \\x2 + ay2 + 1 is continuous everywhere. i) Let f : R2 - R and suppose that lim f(x, y) = 5. (x, y) -(1,3) What can you say about the value f(1, 3)? j) What is the curvature of r(t) = (2 + 3t, 7t, 5 - t) at t = In 2