An investor purchased 100 shares of Omega common stock at $80 a share plus $20 commission for the transaction. He held the stock for nine years. For the first four years he received annual end-of-year dividends of $6 per share. For the next five years he received annual dividends of $9 a share. At the end of the ninth year he sold his stock for $120 a share and paid $30 commission. What rate of return did he receive on his investment?