For the year 2023, AT&T Inc. reported the following: total revenue of $140 billion, cost of goods sold of $85 billion, operating expenses of $35 billion, interest expense of $8 billion, and tax expense of $10 billion. The company’s total assets amounted to $270 billion, and its total liabilities were $130 billion.

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