$5-$ Find the diameter & stroke of a $4-$stroke $6-$cylinder internal combustion engine, which

develops $600kW$ at $1500rpm$ with a mechanical efficiency of $0\mathrm{.}85,$ and a specific fuel

consumption of $245\frac{g}{b}kW.hr.$ The fuel used is iso$-$octane $C_8{H}_{18}$ and excess air factor is $1\mathrm{.}5.$

Volumetric efficiency is $80\%$ at $1$ bar and $27C.$ Take $\frac{L}{d}=1\mathrm{.}2.$