$4-99$ The combustion in a gasoline engine may be approximated by a constant$-$volume heat addition process. The cylinder contains the air$-$fuel mixture before

combustion and the combustion gases after it$,$ and both may be approximated as air, an ideal gas. In a gasoline engine, the cylinder conditions are $1\mathrm{.}2$ MPa and

$450C$ before the combustion and $1900C$ after it$.$ Determine the pressure at the end of the combustion process. Answer. $3\mathrm{.}61$ MPa