ABC Company is a producer of electronic furnace air filters. A significant jump in new housing starts in the region has triggered a 25 percent increase in orders for the filter units, especially the quality model that ABC sells for $270. Six weeks after increasing production to supply the increased orders, the production intern questions you about the following cost data:

Filter	This Month	Last Month	Change
Average total cost per unit	$167.20	$171.14	-$3.96
Cost of last unit produced (i.e., marginal cost)	$104.90	$101.22	+$3.68

In the simplest terms possible and using what you have learned about cost behavior, provide a plausible explanation of how this might occur.