For the year 2023, McDonald's Corporation reported total revenue of $60 billion, cost of goods sold of $25 billion, operating expenses of $20 billion, interest expense of $3 billion, and tax expense of $4 billion. The company’s total assets were $110 billion, and total liabilities were $50 billion.

1. Calculate the gross profit margin.
2. Determine the net profit margin.
3. Compute the debt-to-equity ratio.
4. Determine the return on equity (ROE).