$(5$ points$)$ The stocks of Wonka Inc. are expected to sell for $$20$ per share in three years from now.

Wonka has just paid a dividend of $$1\mathrm{.}50$ per share and the dividends are expected to grow at a rate

of $7\%$ per year for the next three years and at a certain constant rate afterwards. Assume the required

rate of return is $15\%.$

a$.$ What is the expected constant growth rate beginning in year $4?$

b$.$ What is the current price for Wonka stock?