I really don't even know where to start on this problem.

I found this formula in the book:

The surface integral of F over S is:

Dbl Integral (Fdot dS)= Dbl Integral (FdotndS)

This is also called the flux ofFacrossS.

and:

Dbl Integral (Fdot dS) = Dbl Integral(Fdot (rsub u Xrsub v) dA

Here is the problem:

Evaluate: Dbl Integral (AdotndS) overSin each of the following cases:

(a)A= yi+ 2xj- zkandSis the surface of the plane 2x + y = 6 in the first octant cut off by the plane z = 4.

(b)A= (x + y^2)i- 2xj+ 2yzkandSis the surface of the plane

2x + y +2z = 6 in the first octant.

The answers are (a) 108. (b) 81.

Thanks a lot! It'd be great if someone could help me out on here by morning or I'm going to have to go talk to a TA for help.