Which of the following statements concerning performance reports is incorrect? The activity level used to populate the flexible budget is based on the actual "units." 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. All material flexible budget variances should be investigated. The master budget variance is equal to the sum of the volume variance plus the flexible budget variance. The master budget and the flexible budget use different cost behavior equation to calculate budgeted expenses