A new proposed investment costs $$89498$ and has installation cost of $$7336.$ The after$-$tax proceeds from selling the old investment are $$51557.$ The after$-$tax annual cashflows from the old investment are equal to $$5344,$ while the after$-$tax cashflows from the new investment are $$16639.$ Assuming both investments have an infinite useful life, what is the payback period for replacing the old investment with a new investment.