NEED THEM right away.

please doesn't have to be perfect.

Let f(x,y) = x3 + y2 - 6xy. (a) Find its partial derivatives fx and fy . (b) Find its second order partial derivatives fxx , fyy , and fxy . (c) Find and classify the critical points of f. (i.e. classify them into local minima, local maxima, and saddle points.)