DTE Energy Company $($DTE$),$ a utility firm, has been paying dividends for a long time. The firm paid $$3\mathrm{.}5$ last year $(D_0=$$$3\mathrm{.}5).$ It is

expected that the firm will increase dividends at a constant growth rate of $4\%.$ The stock is currently selling for $$123.$ What is the

cost of $($common$)$ equity?

Cost of equity $=,\%$