$13.$ An investor buys $$8,000$ worth of a stock priced at $$40$ per share using $50\%$ initial margin. The broker charges $6\%$ on the margin loan and requires a $30\%$ maintenance margin. In one year the investor gets a margin call. At the time of the margin call the stock's price must have been $\_\_\_\_.$

A$.$ $$20\mathrm{.}00$

B$.$ $$29\mathrm{.}77$

C$.$ $$30\mathrm{.}29$

D$.$ $$32\mathrm{.}45$