$\mathrm{PVP}^{-1 / 3}=$ constant

$\mathrm{PV}^{3 / 2}=$ constant

$\Rightarrow x=\frac{3}{2}, \gamma=\frac{5}{3}$

$\mathrm{C}=\frac{\mathrm{R}}{\gamma-1}+\frac{\mathrm{R}}{1-\mathrm{x}}=\frac{3 \mathrm{R}}{2}+\frac{\mathrm{R}}{1-\frac{3}{2}}=-\frac{\mathrm{R}}{2}$

$\mathrm{C}$ is negative $\Delta Q=n C \Delta T$

$\Rightarrow$ if $\Delta Q$ is $+v e, \Delta T$ is$ -$ve

$\Rightarrow$ temperature will decrease