A company reports the following information:

Month	Units Sold	Total Cost
January	900	$ 5,450
February	1,800	$ 6,900
March	2,400	$ 8,100
April	600	$ 3,600

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

a) $1,500.

b) $3,600.

c) $6,000.

d) $3,300.

e) $2,100.