(1 point) Let f(x, y)=xex2−yf(x, y)=xex2−y and P=(6,36)P=(6,36). (a) Calculate ∥∇fP∥‖∇fP‖. (b) Find the rate of change of ff in the direction ∇fP∇fP. (c) Find the rate of change of ff in the direction of a vector making an angle of 45∘45∘ with ∇fP∇fP. Answers : (a) (b) (c)