Assume that my stote has six cans of Hearty Soup in inventory; four cans were purchased at $2.00 per can, while two cans were purchaded at a cost of $2.25 per can. All six cans are available for sale to customers at $3.00 per can.

A customer walks in, purchases a can of soup, and leaves. I ask the cashier "Was that a $2.00 can of soup?" The cashier replies "I dont know - they're exactly the same. Besides, why do you care?"

please explain why the store owner cares which can of soup was sold.