Consider a Carnot engine operating between temperatures T_h_ and T_c_, where T_c_ is above the ambient temperature T_o_. A second engine operates between the temperatures T_c_ and T_o_. Calculate (in terms of temperatures) the overall efficiency of the two-stage engine operating this way, and compare with the efficiency of a single Carnot engine operating between the high and low temperatures T_h_ and T_o_. Which has the higher efficiency, the two-stage or the single engine? e = 1 - (T_c_/T_h_) e_2stage_ = 1 - (T_c_/T_h_)(T_o_/T_c_) = 1 - (T_h_-T_o_)/(T_h_) If I set this up correctly, the 2tage carnot engine will be by far more efficent since it uses the discarded heat to create more work. I have a funny feeling as if this is violating some law of thermodynamics however.. any advice and feedback is much appreciated. Thanks.