Company WWW is identical in all operating and risk characteristics to Company ZZZ. but their capital structures differ. Company WWW and Company ZZZ both pay corporate income tax at 20%

Company WWW has a gearing ratio (debt: equity) of 1:3 Its pre-tax cost of debt is 6%.

Company ZZZ Is all-equity financed. Its cost of equity is 15%

What is the cost of equity tor Company WWW?