(d) Let initial conditions $= V,T$
And final conditions $= V^{'},T'$
By Charle’s law $V \propto T$ [$P$ remains constant]
$\frac{V}{T} = \frac{V^{'}}{T^{'}} \Rightarrow \frac{V}{T} = \frac{V^{'}}{1.2T^{'}} \Rightarrow V^{'} = 1.2V$
But as per question, volume is reduced by 10% means
$V^{'} = 0.9V$
So percentage of volume leaked out
$= \frac{(1.2 - 0.9)V}{1.2V} \times 100 = 25\%$