In 03/2018, the Mayze Corp. sold an issue of common stock in a public offering. The shares sold for $50/share. Mayze's dividend in 2017 was $2.50/share and analysts expect that the firm's earnings and divides will grow at a rate of 5% per year for the foreseeable future. Although the shares sold for $150 per share, Mayze received net proceeds from the issue of only $45 per share. The different represents the floatation cost paid to the investment banker. What is the common stock investor's required rate of return (and the cost of retained earnings)