(b) For path iaf, Q1=50cal,W1=20cal By first law of thermodynamics, ΔU=Q1−W1=50−20=30cal For path ibf Q2=36cal W2=? ΔUibf=Q2−W2 Since, the change in internal energy does not depend on the path, therefore ΔUiaf =ΔUibf ΔUiaf =ΔUibf ⇒30=Q2−W2 ⇒W2=36−30=6 cal.