Addison, Inc. uses a perpetual inventory system. Below is information about one inventory item for the month of September. 20 units at $20 Sep. 1 Inventory 4 Sold 10 Purchased 17 Sold 10 units 30 units at $25 20 units 30 Purchased 10 units at $30 If Addison uses LIFO, the September 30 inventory balance is Oa. $650 Ob. $800 Oc. $750 Od. $700