For a thermodynamic system, change in internal energies in processes is function of states only, i.e. it depends only on their initial state and final state and completely independent from the thermodynamic paths through which system has been taken. So, in the ligure given in question, for processes I and II initial and final states are same, therefore change in internal energies will also be same for both processes I and II. i.e. ∆U1=∆U2