Underfoot Products uses standard costing. The following information about overhead was generated during May: Standard variable overhead rate: $2 per machine hour Standard fixed overhead rate : $1 per machine hour Actual variable overhead costs: $390,000 Actual fixed overhead costs: $175,000 Budgeted fixed overhead costs: $190,000 Standard machine hours per unit produced: 10 Good units produced: 18,000 Actual machine hours: 198000 Compute the variable overhead efficiency variance.