The Maxit 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: $24,380

Actual machine-hours worked: 2,400 hours

Variable overhead rate variance: $4,620 U

Total variable overhead spending variance: $6,380 U

The variable overhead efficiency variance for July is: