Let f(x, y) = x³y². a. Find the gradient of f(x, y) at the point (x, y) = ( − 1, 2). Vf(-1, 2) = = (Use angle bracket to write your answer as a vector.) b. Find the unit vector u in the direction of v = ( − 2, 3). Ú = (Use angle bracket to write your answer as a vector.) c. Find the directional derivative of f(x, y) in the direction of at the point ( – 1, 2). Dif(-1,2)=