Which of the following statements concerning performance reports is correct? The actual budget and the flexible budget use the same cost behavior equation to calculate budgeted expenses. The activity level used to populate the master budget is based on the actual "units." All immaterial flexible budget variances should be investigated. The flexible budget variance is equal to the sum of the volume variance plus the master budget variance. A favorable sales revenue flexible budget variance would indicate that the actual sales price was higher than the sales price used in the master budget