How much do you have to deposit today so at the beginning of 11 years from now you can withdraw $15,000 a year indefinitely? Assume a discount rate of 6 percent.

This is the explanation my school gives but it does not make sense to me at all:

Timeline: 0--------------9---10 (first payment; end of year 10 = begin of year 11)------------

First perpetuity payment at end of year 10 so we get PV = C/r for end of year 9 PV9 = C / r = 15,000 / 6% = 250,000

N = 9; I/Y = 6%; PMT = 0; FV = 250,000 PV = 147,974.62

Wouldn't I have to use N as 10 instead of 9?