Fair foul question

[Jay R]

Here is a comment regarding fair and foul balls from the OBR rulebook.

Rule 2.00 (Fair Ball) Comment: If a fly ball lands in the infield between home and first base, or
home and third base, and then bounces to foul territory without touching a player or umpire and before
passing first or third base, it is a foul ball; or if the ball settles on foul territory or is touched by a player
on foul territory, it is a foul ball. If a fly ball lands on or beyond first or third base and then bounces to
foul territory, it is a fair hit.


Here is my question. When a fly ball lands between the mound and second base and then bounces untouched to foul territory between home and first. is the area behind the mound considered beyond first base? I always thought the answer was yes but a fellow ump disagrees. If the answer is no, how far does the ball have to fall to be considered beyond first or third base?