At lunchtime, Pete's Chilly Dogs sells hot dogs, chips, and soft drinks from five portable hot dog carts stationed on busy street corners. The depreciation cost on the carts is $1,000 per year for each cart. The company buys supplies (hot dogs, chips, cups, napkins) as needed. The 5 cart operators are each paid $8,000 per year plus 5% of sales revenue. Relative to the number of customers at a particular hot dog stand, the depreciation cost is