That's all the information given in the problem.

The following income statements are provided for Li Company's last two years of operation:

	2011	2012
Number of units produced and sold	4,100	3,700
Sales revenue	69,700	62,900
Cost of goods sold	(55,760)	(49,960)
Gross margin	13,940	12,940
General, selling and administrative expenses	(12,620)	(11,740)
Net income	$1,320	$1,200

Assuming that cost behavior did not change over the two year period, what is the annual amount of the company's fixed manufacturing overhead?

I know the answer is $8,200. But what I can't figure out is why. This is what I did:

Variable manufacturing overhead cost per unit = (55,760-49,960)/(4,100-3,700)

Variable manufacturing overhead cost per unit = $14.50

The annual amount of the company's fixed manufacturing overhead = 55,760-(14.50*4,100)

The annual amount of the company's fixed manufacturing overhead = 55,760-59,450

The annual amount of the company's fixed manufacturing overhead = -3,690

What am I doing wrong?