Apple Inc. reported the following financial information for the year ending September 30, 2023:

• Total Revenue: $350 billion
• Cost of Goods Sold (COGS): $200 billion
• Operating Expenses: $80 billion
• Other Income: $20 billion
• Tax Expense: $40 billion

a) Calculate the gross profit. b) Determine the operating profit. c) Compute the net profit before tax. d) Calculate the net profit after tax, assuming a tax rate of 15%.