$PV = nRT$

$n =\frac{ m }{ M }$

where

$m =$ weight in grams

$M =$ molecular weight

$PV =\frac{ m }{ M } RT$

$V =\left(\frac{ m }{ P }\right) \frac{ R }{ M } T$

slope of expansion curve is determined by $\left(\frac{m}{P}\right) \frac{R}{M}$

for mass $m$ and pressure $P$ slope

$S _{1}=\left(\frac{ m }{ P }\right) \frac{ R }{ M } \quad$ eq(1)

for mass $2 m$ and pressure $\frac{P}{2}$ slope

$S _{2}=\left(\frac{2 m }{\frac{ p }{2}}\right) \frac{ R }{ M }$

$S _{2}=4\left(\frac{ m }{ P }\right) \frac{ R }{ M } \quad eq (2)$

$\frac{e q(2)}{e q(1)}$

$S _{2}=4 S _{1}$

According to question given

$S _{1}=2$

$SO _{2}=8$