Potential energy at the surface \(=-\frac{G M m}{R}\)
Potential energy at height, \(n R=-\frac{G M m}{(n+1) R}\)
Change in potential energy \(=-\frac{G M m}{(n+1) R}+\frac{G M m}{R}\)
\(=\frac{G M m}{R}\left(\frac{-1+n+1}{n+1}\right)\)
\(=\left(\frac{n}{n+1}\right)\left(\frac{G M}{R^2}\right) m \times R\)
\(=m g R\left(\frac{n}{n+1}\right)\)
$\left\{\frac{4 \pi^{2}}{G}=6 \times 10^{11} {N}^{-1} {m}^{-2} {kg}^{2}\right\}$