(a) Given that A = xyax + yzay + xzaz, evaluate ∫S A ∙ dS, where S is the surface of the cube defined b y 0 < x < l, 0 < y < 1, 0 < z < 1.
(b) Repeat part (a) if S remains the same but A = yzax + xzay + xyaz.