Which of the following statements is CORRECT?

a$.$ The stock valuation model, $PO=D\frac{1}{rs-g},$ can be used to value firms whose dividends are expected to decline at a constant rate, i$.$e$.,$ to grow at a negative rate.

b$.$ The constant growth model cannot be used for a zero growth stock, where the dividend is expected to remain constant over time.

within the next few years.

d$.$ The price of a stock is the present value of all expected future dividends, discounted at the dividend growth rate.

e$.$ If a stock has a required rate of return $r=12\%$ and its dividend is expected to grow at a constant rate of $5\%,$ this implies that the stock's dividend yield is also $5\%.$