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: $25,920 Actual machine-hours worked: 3,100 hours Variable overhead rate variance: $5,670 U Total variable overhead spending variance: $7,920 U The variable overhead efficiency variance for July is: Multiple Choice $2,250 U $13,590 F $2,250 F $13,590 U.