The cost of preferred stock is unaffected by changes in the market price. increases as the price of the stock increases. is equal to the stock's dividend yield. is constant over time increases when a firm's tax rate decreases. Which one of the following statements is correct? Preferred stock is valued using the SML or security market line model Preferred stock is generally the cheapest source of capital for a firm The cost of preferred stock is unaffected by the issuers tax rate The cost of preferred stock remains constant from year to year An increase in the market value of preferred stock will increase a firm's weighted average cost of capital