not sure what im doingfor gross margin using SI

Required information [The following information applies to the questions displayed below.) Hemming Co. reported the following current-year purchases and sales for its only product. Date Activities Units Acquired at Cost Units Sold at Retail Jan. 1 Beginning inventory 285 units @ $13.40 = $ 3,819 Jan. 10 Sales 250 units @ $43.40 Mar. 14 Purchase 470 units @ $18.40 - 8,648 Mar. 15 Sales 400 units @ $43.00 July 30 Purchase 485 units @ $23.40 = 11,349 Oct. 5 Sales 460 units @ $43.40 Oct. 26 Purchase 185 units @ $28.40 = 5,254 Totals 1,425 units $29,070 1,110 units Required: Hemming uses a perpetual inventory system. Assume that ending inventory is made up of 45 units from the March 14 purchase, 85 units from the July 30 purchase, and all 185 units from the October 26 purchase. Using the specific identification method, calculate the following Answer is complete but not entirely correct. a) Cost of Goods Sold using Specific identification Available for Sale Cost of Goods Sold Date Activity Unit Cost Units Units Sold Ending Inventory Ending Ending Unit Inventory Units Cost Inventory Cost Unit Cost COGS Prev 1 of 1 !!! Next Answer is complete but not entirely correct. a) Cost of Goods Sold using Specific identification Available for Sale Cost of Goods Sold Units Unit Sold Cost COGS Ending Inventory Ending Unit Ending Inventory Cost Inventory Units Cost Date Activity Unit Cost Units Jan 1 285 $ 3,819 $ 0 Beginning Inventory Purchase $ 13.40 $ 18.40 0S 13.40 45 $ 18.40 Mar. 14 470 7,820 828 >> July 30 Purchase 485 285 $ 13.40 425 $ 18.40 400 $ 23.40 28.40 1.110 9,360 85 $ 23.40 1.989 23.40 $ 28.40 Oct 26 Purchase 185 0 185 $ 28.40 5,254 8,071 1,425 $ 20,999 315 b) Gross Margin using Specific Identification Cost of goods sold 20,999 Less: Sales 8.071 X Equals: Gross margin 12928