Explanation

(d) Gravitational potential energy of body will be
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E = \frac{GM_{e}m}{r}$
$At\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ r = 2R,$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E_{1} = - \frac{GM_{e}m}{(2R)}$
$At\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ r = 3R$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E_{2} = - \frac{GM_{e}m}{(3R)}\ $
Energy required to move a body of mass $m$ from on orbit of radius $2R\ to\ 3R$ is
$\ \ \ \ \ \ \ \ \ \mathrm{\Delta}E = \frac{GM_{e}m}{R}\left\lbrack \frac{1}{2} - \frac{1}{3} \right\rbrack = \frac{GM_{e}m}{6R}$