need help with a,b,c

Tree Seedlings has the following current-year purchases and sales for its only product. Units Sold at Retail Date Activities Jan. 1 Beginning inventory Jan. 3 Sales Feb.14 Purchase Feb. 15 Sales June 30 Purchase Nov. 6 Sales Nov.19 Purchase Totals Units Acquired at Cost 140 units @ $2 - $ 280 210 units e $3-$ 630 190 units & $4 - $ 760 102 units @ $8 160 units @ $8 146 units e $8 60 units @ $5 - $ 300 600 units $1,970 408 units Required: The company uses a perpetual inventory system. a. Determine the costs assigned to ending inventory and to cost of goods sold using FIFO. b. Determine the costs assigned to ending inventory and to cost of goods sold using LIFO. c. Compute the gross margin for each method