Solarcell Corporation has $20,000 that it plans to invest in marketable securities. It is choosing between AT&T bonds that yield 11.50%, State of Florida municipal bonds that yield 8.00%, and AT&T preferred stock with a dividend yield of 9.50%. Solarcell's corporate tax rate is 25%, and 50% 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.