where did the 2.30 come from? why is E+D=1+1.3????

what is the 1 and why is it 1???????????????

15-12. Summit Builders has a market debt-equity ratio of 1.30, a corporate tax rate of 38%, and pays 9% interest on its debt. The interest tax shield from its debt lowers Summit's WACC by what amount? D 1.30 E+D 2.30 = = 0.565. Therefore, WACC = Pretax WACC 0.565(9%)(0.38) = Pretax WACC 1.93% So, it lowers it by 1.93%