Assume the following information for a company:

• There are 6 million ordinary shares. Analysts consider it normal to double your money in four years in this industry. The shares last traded at $11.00 per share.
• An overdraft of $15 million attracts an interest rate of 6% pa compounded monthly.
• 90-day bank bills have just been issued with a Face Value of $20m and yield of 4% pa.
• Bonds exist with a total face value of $30m, a market value of $30m, a coupon of 5% pa paid semi-annually and 10 years to maturity.
• The company accounts show $4m in retained earnings and $3m in trade credit (accounts payable).
• The corporate tax rate is 30%.

Calculate the Weighted Average Cost of Capital on an after-tax basis. Explain and defend your treatment of Retained Earnings and Trade Credit.