"Centra Corp. currently has a gearing ratio of $20\%($based on market values and measured as debt$/($debt $+$ equity$)$ and a WACC of $9\mathrm{.}4\%.$ The corporate income tax rate is $30\%.$ Calculate, using Modigliani and Miller s theory with tax, the theoretical WACC for Centra if gearing was to be increased to $40\%."$