Hickory Furniture Company paid for the following costs during the month of May: Inventory purchases $ 40,000 Advertising costs 8,000 Delivery costs 2,000 Hickory sold $32,000 of the inventory and has agreed to pay warranty expenses for its customers. These are expected to be $1,600 and occur evenly over the next four months (i.e., starting in June). What type of cost is the advertising expense?