Given two endpoints:

and

, the midpoint of the two endpoints

is given by

Thus, given the midpoint L(-1, 8) and one endpoint J(4, -15). The second endpont is given by

i.e.

and
So, the fee is 125 and...
125+
a certain fee "x"
125+x*
which is paid monthly, that is 12 times:
125+x*12
and this equals 720.
125+x*12=720
subtracting 125:
x*12=595
dividing by 12:
x=49,58
and this is how much they pay each month!
The answer is (0,0) to (0, -5) I hope this helped ^^
600
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