12. A cost thait changes in proportion to changes in volume of activity is an A. Diffferential cost B. Fixed cost C. Incremental cost D. Variable cost E. Product cost. 13. A cost with a flat oost line within a relevant range that shifts to another level when volume significantly changes is aln) A. Step-wise cost. B. Fixed cost. C. Curvilinear cost. D. Incremental cost. E. Flat line cost 14. An important tool in predicting the volume of activity, the costs to be incurred, the sales to be made, and the profit to be earned is: A. Target income analysis. B. Cost-volume-profit analysis. C. Least-squares regression analysis D. Variance analysis. E. Process costing