You $($many years ago$)$ are deciding whether to upgrade your

company's equipment from typewriters to computer

technology at a cost of $$2,500$ per machine, and machines

will be replaced one$-$to$-$one. The typewriter technology was

able to output $$8,000$ per unit per year, and you expect the

computers to be able to output $$9,964$ per unit per year

$($forever$),$ but render the typewriters completely worthless.

What would the NPV be of making this upgrade, per

upgraded unit? Assume a $8\mathrm{.}8\%$ interest rate.