Heat flows from a reservoir at 373 K to a reservoir at 273k through a copper rod as shown in the figure. The heat then leaves the 273K reservoir and enters a Carnot engine, which uses part of this heat to do work and rejects the remainder to a third reservoir at 173K.What fraction of the heat leaving the 373K reservoir is rendered unavailable for doing work, as compared to the situation where a Carnot engine is connected directly between the 373K and 173K reservoirs?