I'm a bit confused by this one, and just having a really hard time understanding it.

Monoture Company uses a periodic inventory system. It entered into the following calendar-year purchases and sales transactions. (For specific identification, units sold consist of 600 units from beginning inventory, 300 from the February 10 purchase, 200 from the March 13 purchase, 50 from the August 21 purchase, and 250 from the September 5 purchase.)

Date	Activities	# Units Acquired	Price Per Unit	Total Inventory	# units sold	Price per unit sold	Total Sales
Jan. 1	Beginning Inventory	600	$45.00	$27,000.00
Feb. 10	Purchase	400	$42.00	$16,800.00
Mar. 13	Purchase	200	$27.00	$5,400.00
Mar. 15	Sales				800	$75.00	$60,000.00
Aug. 21	Purchase	100	$50.00	$5,000.00
Sep. 5	Purchase	500	$46.00	$23,000.00
Sep. 10	Sales				600	$75.00	$45,000.00

1. Compute the 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 in 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.