please solve it (thank you)

560 a. Calculate the IRR for each of the three cash-flow diagrams that follow. Use EOY zero for (i) and EOY four for (ii) and (iii) as the reference points in time. What can you conclude about "reference year shift" and "proportionality" issues of the IRR method? b. Calculate the PW at MARR =10% per year at EOY zero for (i) and (ii) and EOY four for (ii) and (iii). How do the IRR and PW methods compare