6. Piper Pipes has the following inventory data: July 1 Beginning inventory 30 units at $120 5 Purchases 180 units at $112 14 Sale 120 units 21 Purchases 90 units at $115 30 Sale 95 units Assuming that a periodic inventory system is used, what is the cost of goods sold on an average unit cost basis. a. $10,992 b. $11,022 C. $30,557 (d) $33,118 6. Piper Pipes has the following inventory data: July 1 Beginning inventory 30 units at $120 5 Purchases 180 units at $112 14 Sale 120 units 21 Purchases 90 units at $115 30 Sale 95 units Assuming that a periodic inventory system is used, what is the cost of goods sold on an average unit cost basis. a. $10,992 b. $11,022 C. $30,557 (d) $33,118