Notice that when you place your coins in the newspaper vending machine that you are then able to open the door and could (although you shouldn't), remove all the newspapers without paying for the additional copies. However, with a soda vending machine, when you place your coins in the machine the door does not open for you to remove your product. Only the item you requested is dispensed. Explain in terms of marginal utility why there is a difference between how both of these products is dispensed.