American Airlines reported the following financial details for 2023. They had a total revenue of $80 million, with a cost of services amounting to $50 million. Their operating expenses were $18 million, and they incurred an interest expense of $4 million and a tax expense of $5 million. The total assets of the company stood at $100 million while the total liabilities were $60 million.

1. Calculate the gross profit margin.
2. Determine the net profit margin.
3. Compute the interest coverage ratio.

Determine the return on equity (ROE).