(b) $PV = \mu\ RT = \frac{m}{M}RT \Rightarrow \frac{m}{VP} \Rightarrow \frac{density}{P} = \frac{M}{RT}$
$\left( \frac{density}{P} \right)_{At\ 0℃} = \frac{M}{R(273)} = x$ …(i)
$\left( \frac{density}{P} \right)_{At\ 100℃} = \frac{M}{R(373)}$ …(ii)
$\Rightarrow \left( \frac{density}{P} \right)_{At\ 100℃} = \frac{273x}{373}$