Walmart Inc. reported the following for 2023: total revenue of $550 billion, cost of goods sold of $400 billion, operating expenses of $100 billion, interest expense of $10 billion, and tax expense of $12 billion. The total assets were $250 billion, and total liabilities were $120 billion.

1. Calculate the operating profit margin.
2. Determine the net profit margin.
3. Compute the interest coverage ratio.
4. Determine the debt-to-equity ratio.