I'm stuck on this partial derivative question.

(a) Express du/dx, du/dy, and du/dz as functions of x, y, and z both by using the chain rule and by expressing u directly in terms of x, y, and z before differentiating. (b) Evaluate du/dx, du/dy, and du/dz at the given point (x,y,z).

u=p-q/q-r, p=6x+6y+6z, q=6x-6y+6z, r=6x+6y-6z; (x,y,z)=(sqrt(3),4,1)