A Diesel cycle has a compression ratio of 20 and begins its compression at 13 psia and

Question:

A Diesel cycle has a compression ratio of 20 and begins its compression at 13 psia and 458F. The maximum cycle temperature is I8008F. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using
(a) Constant specific heats at room temperature and
(b) Variable specific heats.