For polytropic process $$pv^{n} = c$$ for a perfect gas, change in entropy is given by the expression

A

$$\frac{\gamma-n}{\gamma-1}$$ Rin $$\frac{V_{2}}{V_{1}}$$

B

$$\frac{\gamma-n}{\gamma-1}$$ Rin$$ \frac{P_{2}}{P_{1}}$$

C

$$\frac{n-1}{n}$$ Rin $$\frac{V_{2}}{V_{1}}$$

D

$$ C_{v} \left(\frac{\gamma-n}{\gamma-1}\right)$$ Rin $$\frac{T_{2}}{T_{1}}$$