I really dont understand this method. help please!

e. Compute the cost of ending inventory using the Specific Identification method For specific identification, the March 9 sale consisted of 80 units from beginning inventory and 340 units from the March 5 purchase; the March 29 sale consisted of 40 units from the Date Activities Sold Cost Beginning 1-Mar Linventory 50 5-Mar Purchase 55 9-Mar Sales 420 16-Mar Purchase 50 25-Mar |Purchase 62 29-Mar Sales 160 SPEC ID Date Sales 1-Mar 5-Mar 16-Mar 25-Mar Totals f. Compute the cost of ending inventory using the Weighted Average method Date Activities Units Sold Cost Beginning 1-Mar Linventory 100 50 5-Mar Purchase 400 55 9-Mar | Sales 420 16-Mar Purchase 120 60 25-Mar Purchase 200 62 29-Mar | Sales 160 Average Date Sales 1-Mar 5-Mar 16-Mar 25-Mar Totals g. Compute Gross margin for each inventory costing methods FIFO Units Sold price per unit total sales Cost of Goods Sold Gross Margin Ending Inventory