What's the Variable overhead Efficiency variance for the month?

The following standards for variable manufacturing overhead have been established for a company that makes only one product Standard hours per unit of output Standard variable overhead rate 8.1 hours $14.85 per hour The following data pertain to operations for the last month: Actual hours Actual total variable manufacturing overhead cost Actual output 8,600 hours $130,720 1,000 units What is the variable overhead efficiency variance for the month