The following information is available for a company's cost of sales over the last four months.

Month	Units sold		Cost of sales
January	400		$	31,000
February	800		$	37,000
March	1,600		$	49,000
April	2,400		$	61,000

Using the high-low method, the estimated total fixed cost is:

$25,000.

$30,000.

$13,692.

$100,000.

$50,000.