astimating a mortgage. Several years ago Bill got a home mortgage of $110,000 with a term of 30 years at an APR of 9%. Use the Long-Term Estimate/Bound (the book calls this Rule of Thumb 3) to estimate his monthly payment, and compare this estimate with what the monthly payment formula gives. The Long-Term Estimate/Bound states: For all loans, the monthly payment is at least as large as the principal times the monthly interest rate as a decimal. This is a fairly good estimate for a long-term loan with a moderate or high interest rate. (Round your answers to the nearest cent.)