What will be the minimum pressure required to compress $500\;dm^3$ of air at 1 bar to $200\;dm^3$ at $30^{\circ}C?$

Question

$\begin{array}{1 1} (a)\;3\;bar \\ (b)\;4.5\;bar \\ (c)\;6\;bar \\ (d)\;2.5\; bar \end{array}$