EcoGoods Ltd. uses a periodic inventory system. Here are its inventory activities for December:

Date	Activity	Units	Unit Cost
Dec. 1	Beginning Inventory	500	$40
Dec. 6	Purchase	600	$42
Dec. 12	Sale	700	-
Dec. 18	Purchase	300	$45
Dec. 22	Sale	400	-

Specific identification details: The December 12 sale consisted of 300 units from beginning inventory and 400 units from the December 6 purchase. The December 22 sale consisted of 200 units from the December 18 purchase and 200 units from the December 6 purchase.

Required:

1. Compute the ending inventory and COGS using specific identification and FIFO methods.
2. Determine the gross profit using the LIFO method.
3. Evaluate the impact of different inventory costing methods on EcoGoods Ltd.'s liquidity and profitability.