4. A car engine is operating on the Carnot cycle between a temperature range of 300C and 22C and a maximum and minimum pressures of 70 bar and 2.4 bar. Assume air to be the working fluid. 4.1. Sketch the Carnot cycle on a T -S diagram. (2) 4.2. Calculate the thermal efficiency. (2) 4.3. Calculate the work ratio. (14) 5. An automobile tire filled to an initial pressure of 28 bar, and with an internal energy of 1500 kJ, is contained in a well-insulated cylinder of volume 0.06 m3. The tires are allowed to expand until its internal energy is 1400 kJ; the law of expansion is pv2= constant. Calculate 5.1. The work done. (2) 5.2. The final volume. (4) 5.3. The final pressure.