A Diesel cycle has a compression ratio of 22 and begins its compression at 89 kPa and 15°C. The maximum cycle temperature is 1200°C. The properties of air at room temperature are R = 0.287 kPa·m³/kg·K, cₚ = 1.005 kJ/kg·K, cᵥ = 0.718 kJ/kg·K, and k = 1.4. Utilizing air-standard assumptions, determine the thermal efficiency of this cycle using constant specific heats at room temperature.