Brad purchased 10 shares of stock for $10 per share. He paid a $5 commission. One year later, he purchased another 10 shares at $9 per share. Again, he paid a $5 commission. In the second year, his disappoint got the best of him and he sold 10 shares at $7 per share, paying another $5 commission. At the end of third year, Brad liquidated his holdings, paying $5 in commissions at $8 per share. What was his dollar-weighted rate of return?