The Maxwell Corporation has a standard costing system in which variable manufacturing overhead is assigned to production on the basis of standard machine-hours. The following data are available for July:
• Actual variable manufacturing overhead cost incurred: $26,580
• Actual machine-hours worked: 3,400 hours
• Variable overhead rate variance: $6,120 Unfavorable
• Total variable overhead spending variance: $8,580 Unfavorable
The variable overhead efficiency variance for July is: