What is the rate of heat interchange per unit change of volume for a polytrophic process $PV^{n}=C?\left ( \gamma =\frac{c_{p}}{c_{V}} \right )$
(a) $\frac{n-1}{\gamma -1}\times p$
(b) $\frac{\gamma -n}{\gamma -1}\times p$
(c) $\frac{\gamma -1}{n-1}\times p$
(d) $\frac{n-1}{\gamma -n}\times p$