Answer
$-16$
Work Step by Step
As we know that $div F=\dfrac{\partial A}{\partial x}i+\dfrac{\partial B}{\partial y}j+\dfrac{\partial C}{\partial z}k$
Now, we have
$div F=-1-1=-2$
This implies that
$div F=\iiint_R (-2) dA=(-2)[(2)(2)(2)]=-16$