(d) Acceleration due to gravity at a height $h$ form the surface of the earth
$\ \ \ \ \ \ \ \ \ \ \ \ g^{'} = g\frac{1}{\left( 1 + \frac{h}{R} \right)^{2}}$
$Given,\ \ h = 2R$
$\therefore\ \ \ \ \ \ \ g^{'} = g\frac{1}{(1 + 2)^{2}}$
$or\ \ \ \ \ \ g^{'} = \frac{g}{9}$