Richmond Clinic has obtained the following estimates for its costs of debt and equity at various capital structures:

	After-Tax
Percent	Cost of	Cost of
Debt	Debt	Equity
0%		16%
20%	6.6%	17%
40%	7.8%	19%
60%	10.2%	22%
80%	14.0%	27%

What is the firm's optimal (lowest cost) capital structure? Please include an excel formula (if applicable).

A) What percent equity? B) What percent debt?