(d) The periodic time of a simple pendulum is given by,
$T = 2\pi\sqrt{\frac{l}{g}}$
When taken to height $2R$.
$g^{'} = g\left( 1 + \frac{h}{R_{e}} \right)^{2}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = g\left( 1 + \frac{2R}{R} \right)^{- 2} = g(3)^{- 2}$
$\therefore$ $\frac{T_{1}}{T_{2}} = \sqrt{\frac{1}{3^{2}}}$
$\Longrightarrow$ $T_{2} = 3T_{1} \Rightarrow \frac{T_{1}}{T_{2}} = \frac{1}{3}$