The following standards for variable manufacturing overhead have been established for a company that makes only one product: Standard hours per unit of output: 8.1 hours, Standard variable overhead rate: $14.85 per hour. The following data pertain to operations for the last month: Actual hours: 8,600 hours, Actual total variable manufacturing overhead cost: $130,720, Actual output: 1,000 units. What is the variable overhead efficiency variance for the month?
a. $7,600 F
b. $7,600 U
c. $7,425 U
d. $2,835 F