Which of the following statements is correct? a. The stock valuation model, P0=D1/(rsg), can be used for firms which have negative growth rates. b. If a stock has a required rate of return rs=12 percent, and its dividend grows at a constant rate of 5 percent, this implies that the stock's dividend yield is 5 percent. c. The price of a stock is the present value of all expected future dividends, discounted at the dividend growth rate. d. Statements a and c are correct. e. All of the statements above are correct