W {\displaystyle W} is the work done by the system (energy exiting the system as work), Q H {\displaystyle Q_{\text{H}}} is the heat put into the system (heat energy entering the system), T C {\displaystyle T_{\text{C}}} is the absolute temperature of the cold reservoir, and T H {\displaystyle T_{\text{H}}} is the absolute temperature of the hot reservoir.