Boeing Company had the following information for the year 2023:

23. 
    
    • Beginning Inventory: $18 billion
    • Purchases: $60 billion
    • Ending Inventory: $20 billion Calculate: a) Cost of Goods Sold (COGS). b) Inventory Turnover Ratio. c) Days Sales Outstanding (DSO) if the accounts receivable at the beginning of the year were $25 billion and at the end of the year were $30 billion.