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Following are five series of costs A through E measured at various volume levels. Examine each series and identify which is fixed, variable, mixed, step-wise, or curvilinear. Exercise 18-4 Cost behavior identification C1 Series B $2,500 3,100 3,700 4,300 4,900 5,500 6,100 Series D $1,000 1,000 2,000 2,000 3,000 3,000 4,000 Series E $5,000 5,000 5,000 5,000 5,000 5,000 5,000 Volume (Units) Series A Series C 0 0 3,600 7,200 10,800 14,400 18,000 21,600 6,000 6,600 7,200 8,200 9,600 13,500 2 3 4 400 800 1,200 1,600 2,000 2,400 6 7 :4 KA Sheet1 Sheet2 Sheet3