need to buy some filing cabinets. You know that Cabinet X costs $10 per unit and requires six square feet of floor space. Cabinet Y costs $20 per unit and requires eight square feet of floor space. You have been given $140 for this purchase, though you don't have to spend that much. The office has room for no more than 72 square feet of cabinets. Cabinet X provides 8 cubic feet of storage, and Cabinet Y provides 12 cubic feet of storage.