4. A Carnot engine has a cycled as shown in FIGURE 4. FIGURE 4 a. What is the Carnot Cycle? 12 Marks b. What are the thermodynamic processes involved at boundaries AD, BC, AB, and CD? 14 Marks If the engine runs on the Carnot cycle takes 2000 J of heat at 450 K, does some work, and discards some heat at room temperature, how much heat is discarded? What is the thermal efficiency of the engine? 14 Marks d. Prove that the total entropy change in one cycle of the engine in Part (c) is zero. 16 Marks) A Carnot engine is made to operate as a refrigerator. Explain in detail the processes with the aid of pV-diagram in FIGURE 5. 14 Marks P! FIGURE 5