an activity level at 18,000 units total cost equals $99,000, variable cost per unit equals $3.00 and fixed costs total $45000. if total cost increase to $129000 then:

a.) the fixed cost per unit equals $2.50

b.) the activity level increases by 10,000

c.) the total average cost per unit equals $12.50

d.) the activity level increases to 23,455 units