A turbine operates adiabatically with superheated steam entering at 45 bar and 400oC If the exhaust steam

Question:

A turbine operates adiabatically with superheated steam entering at 45 bar and 400oC If the exhaust steam must be "dry," what is the minimum allowable exhaust pressure for a turbine efficiency, ή = 0.75? Suppose the efficiency were 0.80. Would the minimum exhaust pressure be lower or higher? Why