d
\(v_{e}=\sqrt{\frac{2 G M}{R}}=\sqrt{\frac{2 G}{R} \times \frac{4}{3} \pi R^{3} \rho}\)

\(=\sqrt{\frac{8 \pi \mathrm{G} \rho}{3} R^{3}}\)

\(\Rightarrow v_{e} \propto R\)

\(\Rightarrow \frac{v_{e}}{v}=\frac{4 R}{R} \Rightarrow v_{e}=4\, v\)