$($Please solve problem $3$ for variable specific heats$)$

An ideal diesel engine uses air as the working fluid. The volume of the cylinder is

$1200c{m}^3$ at the beginning of the compression process, $75c{m}^3$ at the end, and

$150c{m}^3$ after the heat$-$addition process. The state of air at the beginning of the

compression process is $100$ kPa and $17C.$ Determine $($a$)$ the pressure at the

beginning of the heat$-$rejection process, $($b$)$ the net work per cycle, and $($c$)$ the

mean effective pressure.

Repeat Problem $3$ using constant specific heats at room temperature.