A disc of radius $\frac{a}{4}$ having a uniformly distributed charge $6\mathrm{C}$ is placed in the $x-y$ plane with its centre at $\left(-\frac{a}{2},0,0\right)$ Fig. 3.78. A rod of length $a$ carrying a uniformly distributed

 

charge $8C$ is placed on the $X-$axis from $x=\frac{a}{4}$ to $x=\frac{5a}{4}$. Two point charges $-7C$ and $3C$ are placed at $\left(\frac{a}{4},-\frac{a}{4},0\right)$ and $\left(-\frac{3a}{4},\frac{3a}{4},0\right)$ respectively. Consider a cubical surface formed by the six surfaces $x=\pm \frac{a}{2},y=\pm \frac{a}{2},z=\pm \frac{a}{2}$. The electric flux through the cubical surface is