Final answer:
The APR of a loan is calculated using the amount borrowed, repayment period, and monthly payment amount. Typically, a financial calculator or the 'RATE' function in spreadsheet software is used to derive the APR from these figures.
Step-by-step explanation:
The question relates to calculating the Annual Percentage Rate (APR) of a loan given the amount borrowed, the repayment period, and the monthly payment amount. Using the provided data: a house costs $139,000, and it is to be paid off in ten years with monthly payments of $1,599.62, we would use a financial calculator or loan amortization formula to find the APR. Unfortunately, this calculation cannot be done with simple interest formulas or without a financial calculator since it involves deriving an interest rate from a payment stream, which usually requires iterative methods or specific financial functions.
As an example to demonstrate how the process may work, we might use the present value formula to find out Joanna's maximum loan affordability given a 4.2% annual interest rate for 30 years. To calculate the exact APR, you would typically use the 'RATE' function in spreadsheet software or a financial calculator.