One way to estimate a firm's cost of debt is by observing the O 1) yield-to-maturity on the firm's outstanding bonds O2) firm's bank borrowing rate on short-term loans O 3) risk-free rate and subtracting a risk premium to the yield on existing debt 4) yield-to-maturity on the newly-issued debt of other firms without regard to risk 5) coupon rate on the outstanding debt of other firms in higher risk classes