Let ΔU1 and ΔU2 be the change in internal energy in process A and B respectively, ΔQ be the net heat given to the system in process (A+B) and ΔW be the net work done by the system in the process (A+ B).
i) ΔU1+ΔU2=0
ii) ΔU1−ΔU2=0
iii) ΔQ+ΔW=0
iv) ΔQ+ΔW=0