Solarcell Corporation has $$20,000$ that it plans to invest in marketable securities$.$ It is choosing between AT&T bonds that yield $11\mathrm{.}00\%,$ State of Florida municipal bonds that yield $8\mathrm{.}00\%,$ and AT&T preferred stock with a dividend yield of $9\mathrm{.}00\%.$ Solarcell's corporate tax rate is $39\mathrm{.}00\%,$ and $70\mathrm{.}00\%$ of the preferred stock dividends it receives are tax exempt. Assuming that the investments are equally risky and that Solarcell chooses strictly on the basis of after$-$tax returns, which security should be selected? Answer by giving the after$-$tax rate of return on the highest yielding security.

$$ a$.8\mathrm{.}24\%$

b$.8\mathrm{.}00\%$

c$.7\mathrm{.}44\%$

d$.6\mathrm{.}08\%$

e$.9\mathrm{.}12\%$