21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, and 32 Evaluate the surface integral F . dS for the given vector field F and the oriented surface S. In other words, find the flux of F across S. For closed surfaces, use the positive (outward) orientation. 21. F (x, y, z) = zey i - 3ze* j+ xyk, Sis the parallelogram of Exercise 5 with upward orientation Answer + 22. F (x, y, z) = zityj+ x k, S is the helicoid of Exercise 7 with upward orientation 23. F (x, y, z) = xy i+ yz j + zx k, S is the part of the paraboloid z = 4 -z - y that lies above the square 0