When determining the optimal capital structure, a. the level of operations does not remain constant. O b. a firm must issue all debt or all equity. c. as the debt level increases, the interest expense must decrease. O d. the assumption is made that the company changes. its capital structure by substituting debt for equity.

When determining the optimal capital structure, a. the level of operations does not remain constant. b. a firm must issue all debt or all equity. c. as the debt level increases, the interest expense must decrease. d. the assumption is made that the company changes its capital structure by substituting debt for equity