The following standards for variable manufacturing overhead have been established for a company that makes only one product: Standard hours per unit of output 4.10 hours Standard variable overhead rate $11.45 per hour The following data pertain to operations for the last month: Actual hours 8,500 hours Actual total labor cost $95,870 Actual output 2,000 units What is the variable overhead efficiency variance for the month? (Do not round intermediate calculations.) $3,435 U $2,652 U $7,133 F $7,133 U