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

MonthUnits SoldTotal CostsJanuary540$ 29,400February760$ 35,000March1,400$ 47,000April2,540$ 59,000

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

Select one:

a. $42,816.

b. $21,408.

c. $29,600.

d. $23,598.

e. $85,632.