Which among the following relations is/are valid ONLY for reversible process undergone by a pure substance?

Figure below shows a reversible heat engine $${E_R}$$ having heat interactions with three constant temperature systems. Calculate the thermal efficiency of the heat engine.

The equivalent evaporation $$(kg/hr)$$ of a boiler producing $$2000$$ $$kg/hr$$ of steam with enthalpy content of $$2426$$ $$kJ/kg$$ from feed water at temperature $${40^ \circ }C$$ (liquid enthalpy $$=168$$ $$kJ/kg$$) is (Enthalpy of vaporization of water at $${100^0}C = 2258$$ $$kJ/kg$$).

In a single stage single row impulse turbine, the steam is entering at a velocity of $$1200$$ $$m/s$$ with a nozzle angle of $${20^ \circ }$$ and leaving the blade in the axial direction. The ratio of blade velocity to the tangential (whirl) velocity of steam is $$0.6.$$ Sketch the velocity diagram and calculate the work output.