The Shrives Corporation has $10,000 that it plans to invest in marketable securities. It is choosing among AT&T bonds, which yield 7.5 percent, state of Florida mu ni bonds, which yield 5 percent, and AT&T preferred stock, with a dividend yield of 6 percent. Shrieves’s corporate tax rate is 35 percent, and 70 percent of the dividends received are tax exempt. Assuming that the investments are equally risky and that Shrieves chooses strictly on the basis of after-tax returns, which security should be selected? What is the after-tax rate of return on the highest-yielding security?