Mark would like to purchase a stock priced at $80. The stock is not expected to pay any dividends in the coming year. He can either put up the entire amount and purchase the stock, or borrow $35 from his brokerage firm at an annual interest rate of 12 percent and put up the remainder. Mark thinks he can sell the stock for $100 after one year. If Mark borrows from his brokerage firm, his estimated return on the stock would be ____ percent.