As for the per-unit cost measures, we see that average fixed cost (AFC) declines steadily over the range of production. This is to be expected, because a constant sum of $100 is being divided by the larger amounts of output. Average variable cost (AVC) declines, reaches a minimum at 4 units of output, and then starts to increase. Average total cost (ATC or AC) behaves in a similar fashion but reaches its minimum point at 6 units of output. Marginal cost declines and then starts to increase once the third unit of output is produced.