Treeline Co. uses a periodic system of inventory. The following information relates to the company's May inventory. Units Unit Cost Total Cost Beginning Inventory 100 $7 $ 700 May 10th purchase 200 $7 $ 1,400 May 20th purchase 300 $8 $ 2,400 Treeline sold 550 units in May, and it uses the average cost method to value inventory. What is the 5/31 ending inventory balance of Treeline's inventory? $ 350. $ 375. O. $ 367. $ 400