Which statements regarding flexible budgeting are true?

Multiple select question.

It involves variable cost items such as direct materials, direct labor, and variable manufacturing overhead.

It is done by multiplying the variable cost per unit of each variable cost item by the actual activity level.

The budget allowance for variable costs should be flexed to show the costs that should have been incurred for the actual level of activity.

Flexible budgeting should include an adjustment to the fixed overhead budget.