we know the Carnot's cycle diagram, so A, B, C, D are points regarding the state of the system. Consider a piston with weight on it. -----AB is just making the piston go up Q = W by providing heat no change in internal energy (this is done by lowering some weight on the top of it ) -----BC is stopping the heat supply and lowering some more weight so the pressure decreases as the work is done by the expense of internal energy w = -du -----CD is putting the system on a cooler surface adding the weight we took out in BC so the work was done on the system and the change in internal energy due to that work was converted into heat to the reservoir (cold one) so the heat you gave in AB was given back ----DA: Now you add some more weight the same as you took away in AB this is more work done on the system and the internal energy rises to the same number as it was at point A hence completing the cycle the energy was transferred from the hot reservoir to the cold one and nothing else happened this is was our whacky way to deliver energy and nothing else
What im saying is that total work is zero, also our book gives this equation Q1(heat in) - Q2(heat out) = W, but here Q1 = Q2 so total work is zero.
But in the figure the total work is the area under the curve, please explain what that area under the curve says.