Consider the following equation. f(x, y) = y3/x, p(1, 2), u = 1 3 2i + 5 j (a) find the gradient of f. ∇f(x, y) = correct: your answer is correct. (b) evaluate the gradient at the point p. ∇f(1, 2) = correct: your answer is correct. (c) find the rate of change of f at p in the direction of the vector u. duf(1, 2) = incorrect: your answer is incorrect.