Answer:
r = 0.073/12 ≈ 0.0060833...
Explanation:
In the given amortization formula, the interest rate (r) is the rate for one payment period.
Period interest rate
The given 7.3% interest rate is presumed to be a nominal annual interest rate. Since there are 12 months in a year, the corresponding monthly interest rate is ...
7.3%/12 = 0.073/12 ≈ 0.00608333...(repeating)
The value of r that goes in this formula is 0.0608333...(repeating).