Following are four series of costs measured at various volume levels. Identify each series as either fixed, variable, mixed, or step-wise. Hint: It can help to graph each cost series.

Volume (Units)	Series A	Series B	Series C	Series D
0	$ 1,140	$ 0	$ 5,140	$ 2,640
400	1,140	3,740	5,140	3,240
800	2,280	7,480	5,140	3,840
1,200	2,280	11,220	5,140	4,440
1,600	3,420	14,960	5,140	5,040
2,000	3,420	18,700	5,140	5,640
2,400	4,560	22,440	5,140	6,240

Following are four series of costs measured at various volume levels. Identify each series as either fixed, variable, mixed, or step-wise. Hint. It can help to graph each cost series