please answer my question

I got 9000 and is wrong

and 3600 is wrong too

Robert Langdon Corp. began the fourth quarter with 1,000 items of inventory that it had previously purchased for $12.50 each ($12,500 total cost). During the fourth quarter, Langdon purchased an additional 900 items of inventory $15 each ($13,500 total cost). Later in the fourth quarter, Langdon sold 1,300 items for $20 each, which was the only sale during the quarter. What is Langdon's inventory balance at the end of the year? Langdon uses the FIFO cost flow assumption. (just enter the number, without any commas or a dollar sign)