The potential (in volts ) of a charge distribution is given by \(V(z)\, = \,30 - 5{z^2}for\,\left| z \right| \le 1\,m\) \(V(z)\, = \,35 - 10\,\left| z \right|for\,\left| z \right| \ge 1\,m\) \(V(z)\)  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

1. A \({\rho _0}\, = \,20\,{\varepsilon _0}\) in the entire region
2. B \({\rho _0}\, = \,10\,{\varepsilon _0}\) for \(\left| z \right|\, \le 1\,\,m\)  and \(P_0 = 0\) elsewhere
3. C \({\rho _0}\, = \,20\,{\varepsilon _0}\) for \(\left| z \right|\, \le 1\,\,m\)  and \(P_0 = 0\) elsewhere
4. D \({\rho _0}\, = \,40\,{\varepsilon _0}\) in the entire region