Can someone please explain these in detail? This is part of my study guide for my first test this week.

The following balance sheet and income statement for Central Manufacturing Corporation will be needed for the next three questions Income Statement Balance Sheet Assets $1,500 8,000 7,500 15.000 14.000 S57,500 (33.500) 24,000 (20,000) (1.000 3,000 (450) 2,550 (850) as Accounts Receivable Inventories Sales (all credit) Cost of Goods Sold Operating Expenses Depreciation an Other Fixed Assets Interest Expense Liabilities & Owners' Equit Accounts Payable Long Term Debt Common Stock Retained Earnings 3,800 5,400 30,000 6,800 Iaxes 19. What is Central's net profit margin? c) 3.7% d) 7.08% a) 4.43% e) 2.96% b) 5.22% What is Central's return on equity? a) 4.03% 20. c) 6.93% d) 4.62% e) 3.7% b) 5.67% 21. Calculate Central's operating income return on investment c) 5.54% d) 8.7% a) 6.52% e) 3.7% 52.17% b) Which of the following is true regarding the over-the-counter market? 22. a) The OTC market is not regulated by the SEC. b) The OTC market includes most security exchanges c) The OTC brokers and dealers are linked by NASDAQ d) The OTC market is a primary mark e) All of the above are true 23. When a new issue of securities is marketed to a definite and select group of investors, such as the firm's employees or current stockholders, the issue is called a(n) a) private placement b) direct sale c) underwritten issue d) best efforts issue e) privileged subscription