Which of the following statements is CORRECT?

a$.$ The maximum federal tax rate on corporate income is $50\%.$

b$.$ Interest paid to an individual is counted as income for tax purposes and taxed at the individual's regular tax rate, but dividends received are taxed at a maximum rate of $20\%.$

c$.$ The maximum federal tax rate on personal income can exceed $50\%.$

d$.$ Corporations obtain capital for use in their operations by borrowing and by raising equity capital, either by selling new common stock or by retaining earnings. The cost of debt capital is the interest paid on the debt, and the cost of the equity is the dividends paid on the stock. Both of these costs are deductible from income when calculating income for tax purposes.

e$.$ Since companies can deduct dividends paid but not interest paid, our tax system favors the use of equity financing over debt financing, and this causes companies' debt ratios to be lower than they would be if interest and dividends were both deductible.