Terrific Toys Company manufactures and sells children's skateboards. Each skateboard requires four bearings. For September, Terrific Toys Company has budgeted skateboard sales of 540 skateboards, while 600 skateboards are scheduled to be produced. Terrific Toys Company will begin September with 200 bearings in its beginning inventory, and estimates ending inventory for September to be 440 bearings. How many bearings should Terrific Toys Company purchase in September?