Please explain

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

Month	Units Sold	Total Cost
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:

Multiple Choice

$25,000.

$30,000.

$13,692.

$100,000.

$50,000.