VzdS where S is the surface of the sphere x2 + y + z = 4 above S z = 1. 2. (x2z + y z)dS where S is the portion of the plane z = 4 + x + y inside S the cylinder x2 + y2 = 4. 3. f(x, y, z) = x - y where S is given by z = ty for 0