Answer:
3.567%
Step-by-step explanation:
There are formulas for all of the variables in a loan amortization except the interest rate. That must be found using a financial calculator, spreadsheet formula, or iterative procedures. Here, we found the value using a graphing calculator.
The interest rate was 3.567% per year.
_____
Additional comment
That interest rate gives a 6th-year balance of $1236.31. The rate is closer to ...
3.5674%
The formula for the balance is ...
A = P(1 +r/n)^(nt)
where principal P is earning interest at rate r compounded n times per year for t years.
The graph shows the value of r (in percent) that makes this difference zero:
f(r) = 1236.34 -1000(1 +r/2)^(2·6)
