4. When the level of activity increases, total fixed costs

a. Decrease

b. Remain the same within the relevant range

c. Decrease inversely with the change in activity

d. Increase within the relevant range

13. Window Shine provides window cleaning service. Information concerning costs and number of windows cleaned for three months during 2017 appear below:

Month	Activity	Cost
May	18,000 windows	$84,000
July	21,000 windows	94,500
September	20,400 windows	94,800

Using the high-low method, what is the amount of total fixed costs?

a. $10,500

b. $3,000

c. $21,000

d. $78,857