Set up 2 PV calculations.
1. rate = .0312 nper = 20 pmt = -3960 fv = 0 type = 0/blank for ordinary annuity (pmt at end of period) or 1 for annuity due (pmt at beginning of period)
This will yield the present value of this string of payments that begins in 18 yrs (58,266).
Now discount this back to today with another PV calculation.
2. rate = .0312 nper = 18 pmt = 0 fv = -58,266 (PV from #1) type = 0
PV = 33,515
(this is all in nominal dollars, ignoring inflation)
We are, as I have said, one equation short. – Keynes