$10-23.($IRR$,$ payback, and calculating a missing cash flow$)$ Wilson Publishing is considering building a printing facility in Sweden that will involve a large initial outlay and then result in a series of positive free cash flows for $4$ years. The estimated cash flows associated with this project are:

$\backslash$table$[[$YEAR$,$PROJECT CASH FLOW$],[0($initial outlay$),?],[1,$$$850$ million$],[2,350$ million$],[3,340$ million$],[4,520$ million$]]$

If you know that the project has a regular payback of $2\mathrm{.}5$ years, what is its internal rate of return?