Koese Inc has a target debt equity ratio of 1.3. Its WACC is 8.4 percent and the tax rate is 40 percent.

If Kose's cost of equity is 13 percent, what is its pretax cost of debt?

my calculation: 8.4%=1*13%+1.3*kd

=5.87 (wrong)

If instead you know that the aftertax cost of debt is 3.7 percent, what is the cost of equity?

my calculation: 8.4% = (1) * cost of equity + (1.3)*.037

=2.91 (wrong)

Please help!