Merck & Co., Inc. had the following financial data for the year ending December 31, 2023:

• Total Assets: $300 billion
• Total Liabilities: $100 billion
• Shareholders' Equity: $200 billion

a) Calculate the debt-to-equity ratio. b) Determine the return on assets (ROA), assuming the net income for the year is $40 billion. c) Compute the return on equity (ROE), assuming the net income for the year is $40 billion.