The following labor standards have been established for a particular product: Standard labor-hours per unit of output 9.3 hours Standard labor rate $13.10 per hour The following data pertain to operations concerning the product for the last month: Actual hours worked 7,100 hours Actual total labor cost $90,170 Actual output 1,000 units What is the labor efficiency variance for the month? $31,660 U $31,660 F $28,820 F $27,940 F