An electric field E =4 x i -(y^2+1) j N / C passes through the box shown in figure. The flux of the electric field through surfaces ABCD and BCGF are…

An electric field $\displaystyle \overrightarrow{\mathrm{E}}=4 x \hat{i}-\left(y^2+1\right) \hat{j} \mathrm{~N} / \mathrm{C}$ passes through the box shown in figure. The flux of the electric field through surfaces ABCD and BCGF are marked as $\displaystyle \phi_{\mathrm{I}}$ and $\displaystyle \phi_{\mathrm{II}}$ respectively. The difference between $\displaystyle \left(\phi_{\mathrm{I}}-\phi_{\mathrm{II}}\right)$ is (in $\displaystyle \mathrm{Nm}^2 / \mathrm{C}$ ) \_\_\_\_.