Charge is distributed non-uniformly in the volume of a solid insulating sphere of radius 'a' such that volume charge density ($\mathrm{\rho }$) varies with distance from the centre (r) as $\mathrm{\rho }$ (r) = ${\mathrm{Cr}}^2$, $\mathrm{r} \le \mathrm{a}$ here C is a constant. Magnitude of electric field strength outside the sphere, i.e., for r > a, is : 

• A

  $\frac{{\mathrm{Ca}}^5}{5{\mathrm{e}}_0{\mathrm{r}}^2}$

• B

  $\frac{{\mathrm{Cr}}^3}{5{\mathrm{e}}_0}$

• C

  $\frac{{\mathrm{Cr}}^2}{2{\mathrm{e}}_0}$

• D

  $\frac{{\mathrm{Ca}}^3}{{\mathrm{e}}_0{\mathrm{r}}^2}$