4. Assuming that a firm pays tax at 50 percent, compute the after-tax cost of capital in the following cases: a) A 10.5 percent preference share sold at par. b) A perpetual bond sold at par, coupon rate of interest being 7 percent. c) A preference share sold at 100 with a 9 percent dividend and a redemption price of 110 if the company redeems it in 5 years. d) An ordinary share sells at a current market price of 120 and pays on a current dividend of 9 per share which is expected to grow at an 8 percent rate