You have $3$ projects with the following cash flows: $($Click on the following icon $$ in order to copy its contents into

a spreadsheet.$)$

a$.$ For which of these projects is the IRR rule reliable?

b$.$ Estimate the IRR for each project $($to the nearest $1\%).$

c$.$ What is the NPV of each project if the cost of capital is $5\%?20\%?50\%?$