Following are five series of costs A through E measured at various volume levels. Identify each series as either fixed, variable, mixed, step-wise, or curvilinear Volume Series E (Units) Series A Series B Series C Series D $ 2,500 3,100 1,000 1,000 2,000 2,000 3,000 3,000 4,000 $5,000 5,000 3,600 7,200 400 6,000 5,000 5,000 5,000 5,000 800 3,700 4,300 6,600 7,200 8,200 9,600 13,500 1,200 1,600 10,800 14,400 18,000 21,600 4,900 5,500 6,100 2,000 2,400 5,000 Series A Series B Series C Series D Step-Wise cost Series E Mixed cost Curvilinear cost Variable cost