Need the answer for preferred stock

The Omega Corporation has some excess cash it would like to invest in marketable securities for a long-term hold. Its Vice-President of Finance is considering three investments: (a) Treasury bonds at a 7 percent yield; (b) corporate bonds at a 13 percent yield; or ( c ) preferred stock at an 9 percent yield. Omega Corporation is in a 40 percent tax bracket and the tax rate on dividends is 10 percent. a-1. Compute the aftertax yields for the three investment options. (Do not round intermediate calculations. Input your answers as a percent rounded to 2 decimal places.) Answer is complete but not entirely correct. a-2. Which one of the three investments should she select based on the aftertax yields? Preferred stock Treasury bonds Corporate bond