The following data pertain to activity and costs for two months:

June

July

Activity level in units

10,000

20,000

Variable costs

$20,000

?

Fixed costs

15,000

?

Mixed costs

10,000

?

Total costs

$45,000

$70,000

Assuming that these activity levels are within the relevant range, what were the mixed costs for July?

Select one:

a. $15,000.

b. $40,000.

c. $35,000.

d. $10,000.