I have this assignment due this week, I've been working at it for like 1 week but I can not figure out how the inventories are supposse to be posted, please help!

The beginning invertory at Continental Office Supplies and data on purchases and sales for the three-month period are as follow:

Jan, 1 Inventory 50 $20 1000
7 Purchase 200 $22 4400
20 sale 90 $40 3600
30 sale 110 $40 4400
Feb, 8 sale 20 $44 880
10 Purchase 130 $23 2880
27 sale 90 $42 3780
28 sale 50 $45 2250
Mar, 5 Purchase 180 $24 4320
13 sale 90 $50 4500
23 Purchase 100 $26 2600
30 sale 80 $50 4000

record the inventory, purchases and cost of merchandise sold for data in a perpetual inventory.

determine total sales and cost of merchandise sold
determine gross profit
determine the ending inventory cost