I need help please!! possible explain too. i dont hnderstand what im dojng wrong!!

Problem 5-4AA (Algo) Periodic: Alternative cost flows LO P3 Montoure Company uses a periodic inventory system. It entered into the following calendar-year purchases and sales transactions. Required: 1. Compute cost of goods available for sale and the number of units available for sale. 2. Computo the number of units in ending inventory. 3. Compute the cost assigned to ending inventory using (a) FIFO, (b) LIFO, (c) weighted average, and (d) specific identification. For specific identification, units sold consist of 700 units from beginning inventory, 400 from the February 10 purchase, 300 from the March 13 purchase, 150 from the August 21 purchase, and 450 from the September 5 purchase. (Round your average cost per unit to 2 decimal places. Round your final answers to the nearest whole dollar amount.) A Answer is complete but not entirely correct. 4. Compute gross profit earned by the company for each of the four costing methods, (Round your average cost per unit to 2 decimal places. Round your final answers to the nearest whole dollar amount.)