Mercedes Brow starts a merchandising business on December 1 and enters into three inventory purchases: December 7 10 units @ $ 9 cost December 14 20 units @ $10 cost December 21 15 units @ $12 cost Mercedes sells 18 units for $35 each on December 15. Seven of the sold units are from the December 7 purchase and eleven are from the December 14 purchase. Mercedes uses a perpetual inventory system. Determine the costs assigned to the December 31 ending inventory when costs are assigned based on (a) weighted average, and (b) specific identification.