(c) $g = \frac{GM}{R^{2}}\therefore g \propto \frac{M}{R^{2}}$
According to problem $M_{p} = \frac{M_{e}}{2}$ and $R_{p} = \frac{R_{e}}{2}$
$\therefore\frac{g_{p}}{g_{e}} = \left( \frac{M_{p}}{M_{e}} \right)\left( \frac{R_{e}}{R_{p}} \right)^{2} = \left( \frac{1}{2} \right) \times (2)^{2} = 2$
$\Rightarrow g_{p} = 2g_{e} = 2 \times 9.8 = 19.6\ m/s^{2}$