part and a b please

Arbitrary FirmName Ltd has a target debt-equity ratio of 1.20. Its weighted average cost of capital (WACC) under a classical tax system is 6.40% and the corporate tax rate is 40.00%. A) If Arbitrary FirmName's cost of equity is 11.40%, what is their pre-tax cost of debt? B) If Arbitrary FirmName's after-tax cost of debt is 4.20%, what is their cost of equity