To solve the problem, we can use the formula for the future value of an annuity:
FV = PMT * ( (1 + r)^n - 1 ) / r
where:
- PMT is the periodic payment
- r is the periodic interest rate
- n is the number of periods
In this case,
- PMT = $475 (the monthly payment)
- r = the monthly interest rate
- n = 24 (the number of months in the agreement)
We first need to calculate the monthly interest rate. We can find this by dividing the yearly interest rate by 12 months:
r = 18% / 12 months = 0.015
Now we can calculate the future value (FV) of the annuity using the above formula:
FV = $475 * ( (1 + 0.015)^24 - 1 ) / 0.015 = $13,237.19
This is the amount that Christopher would owe after 24 months if he made monthly payments of $475.
However, Christopher pays off the loan after 18 months. To find out how much he owes at this point, we can calculate the future value after 18 months:
FV = $475 * ( (1 + 0.015)^18 - 1 ) / 0.015 = $10,198.66
So, after 18 months, Christopher owes approximately $10,198.66.