AutoParts Co. uses a periodic inventory system. The following inventory transactions occurred in March:

• March 1: Beginning Inventory, 150 units @ $75 each
• March 7: Purchased 450 units @ $78 each
• March 15: Sold 500 units @ $120 each
• March 20: Purchased 300 units @ $80 each
• March 27: Sold 350 units @ $130 each

For specific identification, the March 15 sale consisted of 100 units from beginning inventory and 400 units from the March 7 purchase. The March 27 sale consisted of 200 units from the March 20 purchase and 150 units from the March 7 purchase.

Required:

1. Calculate the ending inventory and COGS using FIFO and LIFO methods.
2. Determine the gross profit using the weighted average cost method.
3. Analyze the impact of inventory costing methods on AutoParts Co.'s liquidity and profitability.
4. Discuss the strategic implications of inventory management for AutoParts Co. and recommend an optimal inventory costing method.