The thermal efficiency of the ideal diesel cycle is given by equation
where $$\rho $$ = Cut off ratio, R = Compression ratio

A. $$\eta = 1 - {1 \over {{R^{r - 1}}}}\left( {{{{\rho ^r} - 1} \over {r\left( {\rho - 1} \right)}}} \right)$$

B. $$\eta = 1 - {1 \over {{R^{r - 1}}}}$$

C. $$\eta = 1 - {1 \over {{R^{r - 1}}}}\left( {{{r\left( {\rho - 1} \right)} \over {{\rho ^r} - 1}}} \right)$$

D. None of the above

Answer: Option A