Biotec has estimated the costs of debt and equity capital for various proportions of debt in its capital structure:

% of Debt	Cost of Debt	Cost of Equity
35	5.4%	13.8%
40	4.6	14.0
45	5.9	14.3
50	6.4	14.7

Based on these estimates, determine Biotecs optimal capital structure.

A. 35% debt

B. 50% debt

C. 40% debt

D. 45% debt