Central Systems desires a weighted average cost of capital of 12 percent. The firm has a before-tax cost of debt of 5 percent and a cost of equity of 15.2 percent. What debt-equity ratio is needed for the firm to achieve its targeted weighted average cost of capital if the tax rate is 20%?

a. 0.67

b. 0.56

c. 0.60

d. 0.40

e. 1.78