A disk of radius (a)/(4) having a uniformly distributed charge 6 C...

A disk of radius $\frac{a}{4}$ having a uniformly distributed charge $6 \mathrm{C}$ is placed in the $x-y$ plane with its centre at \left(\frac{-a}{2}, 0,0\right)$. A rod of length a carrying a uniformly distributed charge$8 \mathrm{C}$is placed on the$x$-axis from$x=\frac{a}{4} to x=\frac{5 a}{4}$. Two point charges$-7 \mathrm{C}$and$3 \mathrm{C}$are placed at$\left(\frac{a}{4}, \frac{-a}{4}, 0\right)$and \left(\frac{-3 a}{4}, \frac{3 a}{4}, 0\right)$, respectively. Consider a cubical surface formed by six surfaces $x=\pm \frac{a}{2}, y=\pm \frac{a}{2}, z=\pm \frac{a}{2}$. The electric flux through this cubical surface is