An air at \(15^{\circ} \mathrm{C}\) and 1 bar is compressed adiabatically to 15 bar by an engine working on Otto cycle. The maximum pressure of the cycle is 40 bar. Calculate air standard efficiency, mean effective pressure. Take \(\mathrm{Cv}=0.718 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\) and \(\mathrm{R}=\) \(0.287 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\).