Work = F d

F_{g} = mg

F_{g} = \frac{GM_{1}M_{2}}{r^{2}}

F_{g} = \frac{G M_{E} m}{R_{E}^{2}}

G = \frac{F_{g} r^{2}}{M_{1}M_{2}}

g = \frac{GM_{E}}{R_{E}^{2}}

M_{E} = \frac{g R_{E}^{2}}{G}

Work = ∫_{R_{1}}^{R_{2}} \frac{GM_{1}M_{2}}{r^{2}} dr

Work = ∫ F dx

Work = ∫ F⃗ · d⃗x