Pierce Products Inc. is considering changing its capital structure. Pierce currently has no debt but would like to add some debt to take advantage of low interest rates and the tax shield. Its investment banker has indicated that the pre-tax cost of debt under various possible capital structures would be as follows:

WD	WE	D/E	rD	rd(1 T)	Levered Beta -l	.l	WACC
0	100%	0.00	6.0%
0.2	80%	0.25	7.0%
0.4	60%	0.67	8.0%
0.6	40%	1.50	9.0%

Tax rate = 0.40

RRF = 0.05

U = 0.

8 Market Risk Premium = 0.06

Considering the information above calculate the WACC that maximizes the firm value