Please resolve this and also provide formula

Northwest Utility Company faces increasing needs for capital. Fortunately, it has an Aa3 credit rating. The corporate tax rate is 30 percent. Northwest's treasurer is trying to determine the corporation's current weighted average cost of capital in order to assess the profitability of capital budgeting projects. Historically, the corporation's earnings and dividends per share have increased about 7.6 percent annually and this should continue in the future. Northwest's common stock is selling at $68 per share, and the company will pay a $5.20 per share dividend (D). The company's $104 preferred stock has been yielding 5 percent in the current market. Flotation costs for the company have been estimated by its investment banker to be $2.00 for preferred stock. The company's optimum capital structure is 30 percent debt, 25 percent preferred stock, and 45 percent ommon equity in the form of retained earnings. Refer to the following table on bond issues for comparative yields on bonds of equal risk to Northwest. Yield to Maturity Price Data on Bond Issues Moody's Issue Rating Utilities: Southwest electric power--7 1/4 2023 Aa2 Pacific bell--7 3/8 2025 Aa3 Pennsylvania power & light--8 1/2 2022 A2 Industrials: Johnson & Johnson--6 3/4 2023 Aaa Dillard's Department Stores --7 1/8 2023 A2 Marriott Corp.--10 2015 B2 $ 915.18 895.25 990.66 8.55% 8.33 8.66 840.24 1,000.92 1,055.10 8.56% 8.77 9.33 a. Compute the cost of debt, kd. (Use the accompanying table-relate to the utility bond credit rating for yield.) (Do not round intermediate calculations. Input your answer as a percent rounded to 2 decimal places.) Answer is complete and correct. Cost of debt 5.83 % b. Compute the cost of preferred stock, Kp. (Do not round intermediate calculations. Input your answer as a percent rounded to 2 decimal places.) Answer is complete but not entirely correct. Cost of preferred stock 5.83 % c. Compute the cost of common equity in the form of retained earnings, Ke- (Do not round intermediate calculations. Input your answer as a percent rounded to 2 decimal places.) Answer is complete and correct. Cost of common equity 15.20 % d. Calculate the weighted cost of each source of capital and the weighted average cost of capital. (Do not round intermediate calculations. Input your answers as a percent rounded to 2 decimal places.) Answer is complete but not entirely correct. Weighted Cost Debt 1.75 Preferred stock 1.47 X Common equity 6.84 Weighted average cost of capital 10.06 % >