The compression ratio of a diesel engine is much larger

Question

Show that the thermal efficiency of an ideal Diesel cycle is given by

Where the ratio r_c = V_I/V₂ is called the compression ratio and the ratio r_E = V₃/V₂ is called the expansion atio for a diesel engine. The compression ratio of a diesel engine is much larger than that of a gasoline engine, because there is no preignition as only air is being compressed. Take r_c = 20, r_s = 5, and, ϒ = 1.4 and calculate the thermal efficiency.