Please help with the Question 4 Specific Identification.

Problem 6-3A Perpetual: Alternative cost flows LO P1 Montoure Company uses a perpetual inventory system. It entered into the following calendar-year purchases and sales transactions. Date Activities Units Acquired at Cost Units Sold at Retail Jan. Beginning inventory Feb. 10 Purchase Mar. 13 Purchase ar. 15 Sales Aug. 21 Purchase Sept. 5 Purchase Sept 10 Sales 600 units $45 per unit 400 units $42 per unit 200 units $27 per unit 800 units $75 per unit 100 units850 per unit 500 units $46 per unit 600 units $75 per unit Totals 1,800 units 1, 400 units