21.

a.You deposit a certain amount of money into an account, leave it there and don't add or subtract any money. In 6 years, your money has doubled. The account pays a certain fixed percent annually at the end of each year. What percent does the account pay?

b. Black Office Supplies recently reported $20,000 of sales, $10,000 of operating costs other than depreciation, and $2,000 of depreciation. It had $10,000 of bonds outstanding that carry a 5.0% interest rate, and its federal-plus-state income tax rate was 40%. How much was the firm's earnings after taxes?

c. Brown Office Supplies recently reported $17,000 of sales, $8,250 of operating costs other than depreciation, and $1,750 of depreciation. It had $9,000 of bonds outstanding that carry a 7.0% interest rate, and its federal-plus-state income tax rate was 40%. What is the company's operating profit margin?

D. Patterson Brothers recently reported EBITDA of $7.5 million and net income of $2.1 million. It had $2.0 million in interest expense, and its corporate tax rate is 30 percent. What is Patterson Brothers' charge for depreciation and amortization?