a
$PV = nRT$
$P \Delta V + V \Delta P =0 \quad($ for constant temp. $)$
$P \Delta V = n R \Delta T \quad($ for constant pressure)
$\Delta T =\frac{ P \Delta V }{ nR }$
$\Delta P =-\frac{ P \Delta V }{ V } \quad(\Delta V$ is same in both cases $)$
$\frac{\Delta T }{\Delta P }=\frac{ P \Delta V }{ nR } \frac{ V }{- P \Delta V }=\frac{- V }{ nR }=-\frac{ T }{ P }$
$( PV = nRT )$
$\left(\frac{ V }{ nR }=\frac{ T }{ P }\right) \quad\left|\frac{\Delta T }{\Delta P }\right|=\left|\frac{-300}{2}\right|=150$