If ProPainters paints 12 houses a week, calculate its total cost, average total cost, and marginal cost.

Question:

If ProPainters paints 12 houses a week, calculate its total cost, average total cost, and marginal cost. At what output is average total cost a minimum?
ProPainters hires students at $250 a week to paint houses. It leases equipment at $500 a week. The table sets out its total product schedule.
Labor (students) Output (houses painted per week)
1 ………………………………………………. 2
2 ………………………………………………. 5
3 ………………………………………………. 9
4 ………………………………………………. 12
5 ………………………………………………. 14
6 ………………………………………………. 15