(17B/19B) GPM: initial payment

[Gil]

I find, Werner, your formulation —certainly correct — somewhat confusing:

N: 360 - number of payment periods (30 years, 12 payments per year)
PV: 60000 - present value
I%: 1 - periodic rate (annual rate I%YR=12 divided by NP=12)
NP: 12 - number of payment periods per growth period (a year)
G%: 7.5 - growth rate per growth period
NG: 5 - number of growth periods

We might think wrongly NG=5 months, instead of 5 years, with frequency change in a year = 1.

I suppose your result -474.8251297 is due to rounding, as the correct one should be -474.8251298 (-474.825129768).