q 0 125 250 375 500 625 750

C'(q) 26 24 30 26 23 25 29

a) If the fixed cost is $8500, use the average of left- and right-hand sums to determine the total cost of producing 500 units.
Answer: $

b) How much would the total cost increase if production were increased one unit, to 501 units?
Answer: $