can explain to me how to do it? thanks

Marlow Company uses a perpetual inventory system. It entered into the following calendar-year 2011 purchases and sales transactions. Units Sold at Retail Jan. Date 1 Feb. 10 Mar. 13 Mar. 15 Aug. 21 Sept. 5 Sept. 10 Activities Beginning inventory Purchase Purchase Sales Purchase Purchase Sales Units Acquired at Cost 800 units @ $48.00/unit 400 units @ $44.00/unit 200 units @ $24.00/unit 700 units @ $79.00/unit 360 units @ $64.00/unit 180 units @ $52.00/unit 100 units @ $79.00/unit Totals 1,940 units 800 units Required: 1. Compute cost of goods available for sale and the number of units available for sale. (Omit the "$" sign in your response.) Cost of goods available for sale Number of units available for sale units 2. Compute the number of units in ending inventory. Ending inventory units 3. Compute the cost assigned to ending inventory using (a) FIFO, (b) specific identification-units sold consist of 600 units from beginning inventory and 200 units from the March 13 purchase, and (c) weighted average cost. (Due to rounding, the sum of Cost of Goods Sold and Ending inventory may not equal the Cost of Good available for sales. Round your per unit costs to 2 decimal places. Round your final answers to the nearest dollar amount. Omit the "$" sign in your response.) Ending inventory $ (a) FIFO (b) Specific identification (c) Weighted average cost $ $ 4. Compute gross profit earned by the company for each of the three costing methods. (Round your per unit costs to 2 decimal places and inventory balances and final answer to the nearest dollar amount.Omit the "$" sign in your response.) Gross profit $ (a) FIFO (b) Specific identification (c) Weighted average cost $ $