$6.$ Again, as a consultant to Mr$.$ Businessman, you are asked to rank the proposals by using IRR $($Internal Rate of Return$)$ method. Which project$($s$)$ should be selected under IRR approach? $(12$ Marks$).$ What is the main shortcoming of IRR approach? $(3$ marks$).($Please identify and list all the variables you use in your calculation when you use a calculator. Round your final answer to two decimal points. Ignore all CCA effect on cash flow$).($Total $15$ marks$)$

$7.$ Finally, use NPV $($Net Present Value$)$ method to rank the investment proposals and use Profitability index indicate which is the best one to pursue. $(12$ marks$).$ What is the most challenging aspect of the NPV method? $(3$marks$).($Please identify and list all the variables you use in your calculation when you use a calculator. Round your final answer to two decimal points. Ignore all CCA effect on cash flow$).($Total $15$ marks$)$