Answer
$ -8 \pi$
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
$Flux =\iiint_{o}(x-1) dz dy dx$
Also,
$Flux =\nabla \cdot F=\int_{0}^{2\pi}\int_{0}^{2}\int_{0}^{r^2} (r \cos \theta-1) dz dr d\theta$
This implies that
$\int_{0}^{2 \pi}(\dfrac{32}{5} \cos \theta -4) d\theta = -8 \pi$