$Pv ^3= a$
Differentiating w.r.t to pressure
$v^3+P 3 v^2 \frac{d v}{d P}=0$
$v=-3 \frac{P d v}{d P}=0$
$v=-3 \frac{P d v}{d P}$
$\frac{d P . v}{d v}=-3 P$
$B=-\left(\frac{d P v}{d v}\right)=-(-3 P)=3 P$

Match the following
$\begin{array}{|l|l|} \hline Column\,\,-\,\,1 & Column\,\,-\,\,2 \\ \hline P\,:\,Process\,\,-\,\,I & \,\,A\,\,:\,\,Adiabatic \\ \hline Q\,:\,Process\,\,-\,\,II & \,\,B\,\,:\,\,Isobaric \\ \hline R\,:\,Process\,\,-\,\,III & \,\,C\,\,:\,\,Isochoric \\ \hline S\,:\,Process\,\,-\,\,IV & \,\,D\,\,:\,\,Isothermal \\ \hline \end{array}$

