The NPV and payback period

Suppose you are evaluating a project with the cash inflows shown in the following table. Your boss has asked you to calculate the project's net present value $($NPV$).$ You don't know the project's initial cost, but you do know the project's regular, or conventional, payback period is $2\mathrm{.}5$ years.

The project's annual cash flows are:

$\backslash$table$[[$Year$,$Cash Flow$],[$Year $1,$$$275,000$