F is the three-dimensional vector field defined by F(x,y,z) = (x,y,z). In other terms,
P(x,y,z) = x, Q(x,y,z) = y, R( x,y,z) = z.
Also, the domain D = [0,1]x[0,1]x[0,1] is the solid unit cube, which consists of every (x,y,z) such that
0 <= x="">=><= 1="" and="" 0="">=><= y="">=><= 1="" and="">=><= z="">=><=>=>
The surface S of the cube D consists of six square faces, with normals pointing out of the cube.
Question: Calculate the flux of F across the surface S of the cube D.