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

MonthUnits SoldTotal CostJanuary400$ 31,000February800$ 37,000March1,600$ 49,000April2,400$ 61,000

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

Select one:

a. $50,000.

b. $25,000.

c. $100,000.

d. $13,692.

e. $30,000.