MAA Systems will have EBIT this coming year of $$5$ million. It will also spend $$1$ million on total capital expenditures and increases in net working capital, and have $$2$ million in depreciation expenses. MAA is currently an all$-$equity firm with a corporate tax rate of $27\%$ and a cost of capital of $9\%.$ If the interest rate on its debt is $6\%$ and the EBIT growth rate $3\%,$ how much can MAA borrow now and still have non$-$negative net income this coming year? What is the optimal debt ratio for the firm $($not considering bankruptcy risk$)?$