I thought about doing the divergence theorem, but then quickly noticed nothign differentiated

$\displaystyle \iint_s F.n d\sigma F = zi + j -xyk $and S is the surface cut from the cylinder$\displaystyle {y}^{2 } + {z}^{ 2} =1, z \geqslant 0$. by the planes $\displaystyle x =0, x=2 $