Explanation

(c)
Given initial volume $\left( V_{1} \right) = 300\ cc;$ initial temperature $\left( T_{1} \right) = 27℃ = 300\ K,$ initial pressure $\left( p_{1} \right) = 620\ mm,$ final temperature $\left( T_{2} \right) = 47℃ = 320\ K$ and final pressure $\left( p_{2} \right) = 640\ mm.$ We know from the general gas equation
$\frac{p_{1}V_{1}}{T_{1}} = \frac{p_{2}V_{2}}{T_{2}}$
$\ \ \ \ \ \ \ \ \ \ = \frac{620 \times 300}{300} = \frac{600 \times V_{2}}{320}$
$\ \ \ \ \ \ \ \ \ \ = 310\ cc$
$\left( where,\ V_{2}\ is\ the\ final\ volume\ of\ the\ gas \right)$