Evaluate the surface integral s 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. f(x, y, z) = y i + (z − y) j + x k s is the surface of the tetrahedron with vertices (0, 0, 0), (4, 0, 0), (0, 4, 0), and (0, 0, 4).