[Given : Permittivity of vacuum $\left.\epsilon_{0}=8.85 \times 10^{-12} C ^{2} N ^{-1}- m ^{-2}\right]$
\(E =\frac{\rho r}{3 \epsilon_{0}}, \text { for } r=R\)
\(E=\frac{\rho R}{3 \epsilon_{0}}=\frac{2 \times 6}{3 \times 8.85 \times 10^{-12}}=0.45 \times 10^{12}\,NC ^{-1}\)
\(=45 \times 10^{10}\,N / C\)