Question. If $F = (x^2+y-4)i + 3xyj + (2xz+z^2)k$
Evaluate $\iint(\nabla\times F)\cdot n\ dS$
where $S$ is the surface of the sphere $x^2+y^2+z^2=16$ above the xy-plane.
If we use Gauss Divergence Theorem, then $\nabla\cdot(\nabla\times F)$ will be divergence of curl of F that is $0$. So I'm unable to understand how to proceed in this question.
Kindly guide me for the same. Thank you.