
If another point charge $q_B$ is also placed at a distance $c ( > b) $ the center of shell, then choose the correct statements 
$V(z)\, = \,30 - 5{z^2}for\,\left| z \right| \le 1\,m$
$V(z)\, = \,35 - 10\,\left| z \right|for\,\left| z \right| \ge 1\,m$
$V(z)$ does not depend on $x$ and $y.$ If this potential is generated by a constant charge per unit volume $\rho _0$ (in units of $\varepsilon _0$ ) which is spread over a certain region, then choose the correct statement
Reason : Two equipotential surfaces are parallel to each other.

Given, that $C_1=C_2=C$ and $C_3=C_4=3 C$.