Air in a piston–cylinder device undergoes an internally reversible cycle. That is, the air itself undergoes a reversible set of processes, but irreversible processes (e.g., heat transfer through a finite temperature difference) are possible outside the air in the cylinder. From state 1 at 100° C and 0.75 MPa, the air expands isothermally to 0.15 MPa at state 2. The air then undergoes a constant-pressure process to state 3, from which the air returns to state 1 by an adiabatic process. Determine the thermal efficiency for the cycle and compare your answer to the thermal efficiency of a completely reversible cycle operating between the same maximum and minimum temperatures. Explain the difference.