$8\mathrm{.}17)$ In a reciprocating engine that operates on the Otto cycle, the working fluid is treated as air throughout the cycle and the air$-$gasoline combustion is modeled as an effect of heat addition of $2100$ kJ$/$kg of air. If the compression ratio is $9$:$1$ and the air pressure and temperature at the start of the compression stroke are $90$ kPa and $25$C$,$ find: the temperatures and pressures at each phase of the cycle; its thermal efficiency; and its net specific work output.

$8\mathrm{.}18)$ The engine in the previous problem has been modified to operate with an ethanol$-$based fuel and so the compression ratio has been increased to $11\mathrm{.}5$:$1,$ with air$-$ethanol combustion corresponding to a heat addition at $1650$ kJ$/$kg of air. If the air pressure and temperature at the start of the compression stroke are $90$ kPa and $25$C$,$ find the thermal efficiency and net specific work output of this engine and compare them to the results of the previous $($gasoline engine$)$ problem.

please solve part $8\mathrm{.}18,$ the answers are a thermal efficiency of $62\mathrm{.}4\%$ and net specific work output $1030$ kJ$/$kg$,$ i just dont understand how to get to these answers.