Number 5 worked out please

5. A vendor offers terms of 2/10, n/30. What is the ANNUAL interest rate (rounded) the vendor is charging a buyer who does not pay within 10 days? 3% b. 37% a c. 56% d 108 6. Revenues less cost of goods sold equals: aGross Margin b. Net Profit d. EBIT Gross Net Profit C. EBITDA