J YJ A business planning tool that helps managers predict how changes in costs and sal e s affect profit. (10) A cost that remains unchanged in total amount despite variations in the volume of actway within a relevant range. 18. A cost is one that remains unchanged despite variations in the volume of activity within a relevant range. A_ _ cost is one that changes in proportion to changes in volume of activity. 19. A cost is one that includes both fixed and variable cost components; a cost is one that reflects a step pattern. per unit is 20. Three important assumptions in cost-volume-profit analysis is that (1) constant, (2) per unit is constant, and (3) are constant in total