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: $22,620 Actual machine-hours worked: 1,600 hours Variable overhead rate variance: $3,420 Unfavorable Total variable overhead spending variance: $4,620 Unfavorable

The variable overhead efficiency variance for July is: _______________________________________________