Q15. Consider the function f(x, y) = (x2 + 42) 5/2. (a) [2 points] Compute the partial derivatives fr and fy. Show your work. (b) [2 points] Based on your answers in part (a), compute the partial derivatives fry and fux. Show your work. Recall that fry = (fx)y and fyx = (fy)x- (c) [Bonus: 1 point] State the conclusion of Clairaut's theorem. Does it hold here? (d) [3 points] Find the directional derivative of f in the direction of the vector u = (3, 4) at the point (x, y) = (0, 1/2). You may assume that f is differentiable