When using a flexible budget, a decrease in activity within the relevant range:

A spending variance is the difference between the amount of the cost in the static planning budget and the amount of the cost in the flexible budget.

A revenue variance is the difference between what the total sales revenue should be$,$ given the actual level of activity of the period, and the actual total sales revenue.

A revenue variance is unfavorable if the revenue in the static planning budget is less than the revenue in the flexible budget.