6. Nike, Inc., a prominent sportswear and equipment company, reveals the following financial figures for the fiscal year ending May 31, 20XX:
   • Total revenue: $40 billion
   • Cost of goods sold: $20 billion
   • Selling and administrative expenses: $12 billion
   • Depreciation and amortization expense: $1 billion
   • Earnings before interest and taxes (EBIT): $7 billion
   • Interest expense: $500 million
   • Income tax expense: $1.5 billion

Calculate the subsequent financial ratios for Nike, Inc.:

a) Operating profit margin b) Return on assets (ROA) c) Return on equity (ROE) d) Debt-to-equity ratio