Phoenix Company common stock is currently selling for $20 per share. Security analysts at Smith Blarney have assigned the following probability distribution to the price of (and rate of return on) Phoenix stock one year from now: Price Probability $16 20 24 28 -20% 0% +20% +40% 0.25 0.30 0.25 0.20 Assuming that Phoenix is not expected to pay any dividends during the coming year, determine the standard deviation of possible rates of return on Phoenix stock