a. How much does the firm currently earn per share?
Since, the firm it's going to retain 90% of its earnings, then:
[tex]22\cdot\frac{90}{100}=19.8[/tex]The firm earns $19.8 per share.
b. What proportion of the firm does currently own?
The firm has 40,000 shares and Sarah currently holds 400, so
[tex]\begin{gathered} \text{Percentage is given by the expresion:} \\ \text{Total}\cdot\frac{\text{percent}}{100}=nu\text{mber equals to the percent} \\ \text{Then,} \\ 40,000\cdot\frac{\text{percent}}{100}=400 \\ \text{percent}=\frac{400\cdot100}{40,000} \\ \text{percent}=1 \end{gathered}[/tex]Sarah owns 1% of the shares.
c. What proportion of the firm will Sarah own after the stock dividend?
[tex]\begin{gathered} 400-(400\cdot\frac{10}{100})=360 \\ \text{Then,} \\ 40,000\cdot\frac{perrcent}{100}=360 \\ \text{percent}=\frac{360\cdot100}{40,000} \\ \text{prcent}=0.9 \end{gathered}[/tex]Sarah will own 0.9% of the shares.
d. At what market price would you expect the stock to sell after the stock dividend?