Listed here are three separate series of costs measured at various volume levels. Volume (Units) Series 1 . 0 $ 200 500 260 283 ' _ 580 526 208 _ 566 780 406 _ 580 1,640 _ 580 1,386 _ 536 1,560 _ 580 Examine each series and identify whether it is best described as a xed, variable, or step-wise cost. Hint: It can help to graph each cost series. Series 1 Series 2 Series 3