David Abbot is buying a new​ house, and he is taking out a 30​-year mortgage. David will borrow ​$208,000 from a​ bank, and to repay the loan he will make 360 monthly payments​ (principal and​ interest) of ​$1,349.91 per month over the next 30 years. David can deduct interest payments on his mortgage from his taxable​ income, and based on his​ income, David is in the 30​%tax bracket.

a. What is the​ before-tax interest rate​ (per year) on​ David's loan?

b. What is the​ after-tax interest rate that David is​ paying?