Carnot efficiency is E = 1 - Tc/Th
Which means that not all of the heat put into the system produces work.
So the efficiency of the proposed engine is
1 - (300K / 400K) = 0.25, which means that 25% of the heat put into the engine (taken from the environment) becomes work.
With that...
Homework Statement
An inventor claims to have invented an engine which operates between constant-temperature reservoirs at 400K and 300K. Data on the engine, per cycle of operation:
Qh = 200J
Qc -175J
W = 40J
Th = 400K
Tc = 300K
Of the first and second laws of thermodynamics, which (if...