$\begin{array}{1 1} r_1 =
2.12 \times 10^{-10}\;m,\; r_2 = 4.77 \times 10^{-10}\;m \\ r_1 =
4.77 \times 10^{-10}\;m,\; r_2 = 2.12 \times 10^{-10}\;m \\ r_1 =
2.12 \times 10^{-11}\;m,\; r_2 = 4.77 \times 10^{-11}\;m \\ r_1 =
4.77 \times 10^{-11}\;m,\; r_2 = 2.12 \times 10^{-10}\;m \end{array} $