The mass of the earth is $6 \times 10^{24}\, kg$ and that of the moon is $7.4 \times 10^{22}\, kg$. The potential energy of the system is $-7.79 \times 10^{28}\, J$. The mean distance between the earth and moon is
$(G = 6.67 \times 10^{-11}\, N\, m^2kg^{-2})$