QS 21-1 Cost behavior identification cl Listed here are four series of separate costs measured at various volume levels. Examine each series and identify whether it is best described as a fixed, variable, step-wise, or curvilinear cost. Hint: It can help to graph each cost series. Volume (Units) Series 1 Series 2 Series 3 Series 4 $ 0 o $450 $100 100 450 $ 800 800 800 800 1,600 105 200 450 120 300 2,400 450 1,600 145 400 3.200 450 1,600 190 4.000 450 250 500 600 2,400 2.400 4.800 450 320 Excel Enter data Select: Inst Charts