(c) $g = \frac{GM}{R^{2}};g^{'} = \frac{GM}{R^{'2}} = \frac{GM(100)^{2}}{(99)^{2}R^{2}}$
% increase in $g = \frac{(g^{'} - g) \times 100}{g}$
$= \left( \frac{g'}{g} - 1 \right) \times 100 = \left\lbrack \left( \frac{100}{99} \right)^{2} - 1 \right\rbrack \times 100$
$\left\lbrack \left( 1 + \frac{1}{99} \right)^{2} - 1 \right\rbrack \times 100 \approx 2\%$