A Diesel engine cycle is modeled as if the working fluid is air at all phases of the cycle, with combustion taking place at constant pressure. If the compression ratio is $18$:$1,$ the air pressure and temperature at the start of the compression stroke are $90$ kPa and $25$C$,$ and the maximum temperature in the cycle is $2250$C$,$ find the temperatures and pressures at each phase of the cycle and its thermal efficiency.

the answers are

T$1=90$K$,$ P$1=298$ kPa

T$2=947$K$,$ P$2=514$kPa

T$3=2250$K$,$ P$3=5148$kPa

T$4=1001$ K$,$ P$4=302$kPa

thermal efficiency$=61\mathrm{.}5\%$

how do i get to these answers.