The book value of a firm's debt is 600 and that of its equity is 800. The market value of equity is 1600 and debt has a market value equal to the book value. Assume also that the net operating income of the firm is 80, the interest rate on its debt is 10% and the marginal corporate tax rate is 50%. What is the ROC of the firm? Choose the closest number (unless you think it cannot be determined).

a.2.27%

b.3.64%

c.5%

d.5.71%

e.It cannot be determined from the data