Is this correct?

Griffen Corporation uses a standard costing system. Information for the month of May is as follows: Actual manufacturing overhead costs ($24,000 is fixed) $80,000 Direct labor: Actual hours worked 12,000 hrs. Standard hours allowed for actual production 10,000 hrs. Average actual labor cost per hour $18.00 The factory overhead rate is based on a normal volume of 12,000 direct labor hours. Standard cost data at 12,000 direct labor hours were as follows: Variable factory overhead $48,000 Fixed factory overhead 24,000 Total factory overhead $72,000 What is the variable overhead efficiency variance for Griffen? Oa. $4,000 U Ob. $8,000 U Oc. $2,000 U Od. $20,000 U