a$.$ The level of sales at which revenue exactly equals costs and expenses.b$.$ Costs that remain unchanged despite changes in sales volume.c$.$ The span over which output is likely to vary and assumptions about cost behavior generally remain valid.d$.$ Sales revenue less variable costs and expenses.e$.$ Unit sales price minus variable cost per unit.f$.$ The reduction in unit cost achieved from a higher level of output.g$.$ Costs that respond to changes in sales volume by less than a proportionate amount.h$.$ Operating income less variable costs.