(d) For adiabatic process $pV^{\gamma} = constant$
$\Rightarrow \ \ \ \ \frac{P_{2}}{P_{1}} = \left( \frac{V_{1}}{V_{2}} \right)^{\gamma}$
$\therefore\ \ \ \frac{{\ P}_{2}}{P} = \left( \frac{800}{100} \right)^{5/3}$
$\Rightarrow \ \ \ \ \ \ \ P_{2} = 32\ P$