$($Payback $$period$,$ NPV$,$ PI$,$ and IRR calculations$)$ You are considering a project with an initial cash outlay of $$$$75,000$ and expected free cash flows of $$$$20,000$ at the end of each year for $6$ years. The required rate of return for this project is $6$ percent.

a$.$ What is the$$ project's payback$$ period?

b$.$ What is the$$ project's NPV$?$

c$.$ What is the$$ project's PI$?$

d$.$ What is the$$ project's IRR$?$