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Required information

An ideal diesel engine has a compression ratio of $20$ and uses air as the working fluid. The state of air at the beginning of the compression process is $95$kPa and $20C.$ The maximum temperature in the cycle is not to exceed $2600K.$ The properties of air at room temperature are $c_p=1\mathrm{.}005k\frac{J}{k}g*K,c_V=0\mathrm{.}718k\frac{J}{k}g*K,R=0\mathrm{.}287k\frac{J}{k}g*K,$ and $k=1\mathrm{.}4.$

Determine the thermal efficiency. $($You must provide an answer before moving on to the next part.$)$

The thermal efficiency is $\%.$