Various investment appraisal methods exist, including Net Present Value $($NPV$),$ Payback Period, Average Accounting Return $($AAR$),$ and Internal Rate of Return $($IRR$).$ Although NPV is widely regarded as the most effective and recommended criterion, IRR remains the most commonly used in practice. Can you explain why this is the case? Please list at least two reasons. $($Hint: you could name some advantages of IRR.$)(20\%)$