Why do interest rates on different types of borrowing, such as federal funds and mortgages, tend to track each other and the inflation rate

Western electric has 32,000 shares of common stock outstanding at a price per share of $79 and a rate of return of 13.00 percent. the firm has 7,300 shares of 7.80 percent preferred stock outstanding at a price of $95.00 per share. the preferred stock has a par value of $100. the outstanding debt has a total face value of $404,000 and currently sells for 111 percent of face. the yield to maturity on the debt is 8.08 percent. what is the firm's weighted average cost of capital if the tax rate is 39 percent?