A used machine costs $20,000 to purchase. It has an annual maintenance cost of

$20,000, a salvage value of $5000, and a 10-year life. If the interest rate is 10% per year

compounded annually, what is the present-worth cost of the machine?

PW = -P+SV(P/F, i%, n)

= -20000 + 5000 (P/F, 10%, 10) - 20000(P/A, 10%, 10)

= -20000 + 5000/ (2.5937) - 20000/ (0.16275)

= -140960.12, so present worth cost is $140,960.12

That is F/P value, not P/F (.38554) why?