To increase its market share, Sole Brother Inc. decided to borrow $50,000 for more advertising for its shoe retail line. The loan is to be paid in four equal annual payments with 15% interest. The loan is discounted 12 points. The first 6 "points" are an additional interest charge of 6% of the loan, deducted immediately from what is received from the $50,000 loan. Another 6 points or $3000 of additional interest is deducted as four $750 additional annual interest payments. What is the after-tax interest rate on this loan, if the firm's combined tax rate is 28%?