The Shrieves Corporation has $10,000 that it plans to invest in marketable securities. It is choosing among AT&T bonds (which yield 6.6%), AT&T preferred stock (with a dividend yield of 6.0%), and state of Florida muni bonds (which yield 5% but are not taxable). The federal tax rate is 21% (ignore any possible state corporate taxes). Recall that 50% of dividends received are tax exempt. Find the after-tax rates of return on all three securities after paying federal corporate taxes.