Bay Corp. sold 6,500 units of its product at $50 per unit in year 2009 and incurred operating expenses of $5 per unit in selling the units. It began the year with 900 units in inventory and made successive purchases of its product as follows:
Jan. 1 Beginning Inventory 900 units @ $21 per unit
Feb. 20 Purchase 1950 units @ $22 per unit
May 16 Purchase 1050 units @$25 per unit
Oct. 3 Purchase 700 units @ $ 26 per unit
Dec. 11 Purchase 2750 units @ $27 per unit
Prepare comparative income statements for the three costing method of FIFO, LIFO, and weighted average. Include a detailed cost of goods sold section as part of each statement. The Company uses a periodic inventory system and income tax rate is 40%

Read this first: Expectations for the Homework Help board
Do not simply retype or paste a question from your book or study material

We won't do your homework questions for you.
You were given the assignment for you to learn.

If you come up with your own answer and post it for us to critique that is within reason.

If you have some SPECIFIC questions that you couldn't find or didn't understand, we may help with that.
But this is your assignment, so show us you have at least attempted to complete it on your own.

Thank you.

I reposted my question showing what I did

I reposted my question showing what I did
Bay Corp. sold 6,500 units of its product at $50 per unit in year 2009 and incurred operating expenses of $5 per unit in selling the units. It began the year with 900 units in inventory and made successive purchases of its product as follows:
Jan. 1 Beginning Inventory 900 units @ $21 per unit
Feb. 20 Purchase 1950 units @ $22 per unit
May 16 Purchase 1050 units @$25 per unit
Oct. 3 Purchase 700 units @ $ 26 per unit
Dec. 11 Purchase 2750 units @ $27 per unit
Prepare comparative income statements for the three costing method of FIFO, LIFO, and weighted average. Include a detailed cost of goods sold section as part of each statement. The Company uses a periodic inventory system and income tax rate is 40%

Where... I didn't see it in this post. After a search I see you created a second thread.

You are supposed to respond to the existing thread (which is this one) which would have been sufficient to satisfy the rules ( we have many people that won't attempt it and just want handed the answer which is WHY there is that rule).. I had to ask a moderator to take the time to combine both threads as a result which will happen soon.

Its posted under How do I find ending inventory because my net income is wrong in the homework section

my third post that I have posted under the homwework section
I calculated all the units: total units is $7350
to find my ending inventory I did
Beginning Inventory + purchases- Cost of goods sold = ending inventory
900 + 6450 - 6500= 850 (but that's in units)
Sales... 325,000 (6500*50)
Beginning Inventory... 18900
Purchass... 161,600
Cost of Goods Available... 180,500
Ending Inventory..

This is where I get stumpped because my answer is not working out to the answer in the text book of 80,970 under the FIFO method