Use the Divergence Theorem to evaluate F. ds, where F(x, y, z) = zxi + + cos zj + (xz + y)k and S is the top half of the sphere x + y + z = 4. (Hint: Note that S is not a closed First compute integrals over S, and S,, where S, is the disk x + y 4, oriented downward, and S, = S, U S.)