The risk-free rate of return is 2.5% and the expected return on the market portfolio is 7.9%. Oklahoma Oilco has a beta of 2 and a standard deviation of returns of 18.1%. Oilco's marginal tax rate is 22%. Analysts expect Oilco's net income to grow by 5% per year in the foreseeable future. Floatation costs of issuing new common stock are 3.9%. Using the capital asset pricing model, what is Oklahoma Oilco's cost of retained earnings, in %? Drop the % symbol. E.g., if your an swer is 10.23%, record it as 10.23.