Final answer:
The APR of a 30-year, $300,000 mortgage with monthly payments of $1250 is approximately 3.883%, rounded to three decimal places.
Step-by-step explanation:
To calculate the Annual Percentage Rate (APR) of a mortgage, we need to know the loan amount, term in years, and the monthly payment amount.
In this case, the loan amount is $300,000, the term is 30 years, and the monthly payment is $1,250.
Using an online APR calculator or a financial calculator, we can determine that the APR of this mortgage is approximately 3.883%, rounded to three decimal places.