please provide me with some explanation

E5.3 Prepare cost of sales section. Below is a series of cost of sales sections for companies X, F, L and 5. L02 L Beginninginventory 250 Purchases 1 500 Purchase returns and allowances 40 Net purchases (a) Freightin 110 Cost of goods purchased (b) Cost of goods available for sale 1 820 Ending inventory 310 Cost of sales (c) 120 1 080 (d) 1030 1 230 1 350 (f) 1230 1000 (g) 290 7210 W) 7940 (D 1 450 7490 0) 43590 (M 42090 2240 (D 49530 6230 43300 Required a. Fill in the lettered blanks to complete the cost ofsales sections. b. Explain the purpose of this exercise. (Hint: What is the main skill you have been developing?)