I need help with the 3rd and 4th part of the problem, thank you so much!

Montoure Company uses a periodic inventory system. It entered into the following calendar-year 2016 purchases and sales transactions. Required: 1. Compute cost of goods available for sale and the number of units available for sale. 2. Compute 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 680 units from beginning inventory, 260 from the February 10 purchase, 240 from the March 13 purchase, 90 from the August 21 purchase, and 330 from the September 5 purchase. (Round your average cost per unit to 2 decimal places.) 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.)