I'm having trouble with the periodic inventory system.

Problem 5-4AA Periodic: Alternative cost flows P3 Refer to the information in Problem 5-3A and assume the periodic inventory system is used. 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. (Round all amounts to cents.) 4. Compute gross profit earned by the company for each of the four costing methods in part 3. Analysis Component 5. The company's manager earns a bonus based on a percentage of gross profit. Which method of inventory costing produces the highest bonus for the manager? Date Jan. 1 Feb. 10 Mar. 13. Mar. 15 Aug. 21 Sep. 5 Sep. 10 Activities Beginning Purchase Purchase Sales Purchase Purchase Sales Totals inventory Units Acquired at Cost 600 units $45 per unit 400 units @ $42 per unit 200 units @ $27 per unit 100 units @ $50 per unit 500 units @ $46 per unit 1,800 units Units Sold at Retail 800 units o $75 per unit 600 units o $75 per unit) 1,400 units