Which of the following statements is/are correct?
a. The flexible budget amount for fixed overhead does not change with changes in production, so this amount remains the same regardless of actual production.
b. A fixed cost flexible budget variance is the variance between the actual and budgeted amounts for a fixed cost in a flexible budget.
c. Fixed overhead budget variance is one of the two main components of total fixed overhead variance, the other being fixed overhead volume variance.
d. All of the above.