Steep Enterprises machines heavy-duty brake rotors that are used on commercial airliners. Steep's management developed the following standard costs: Standard direct labor hours per rotor 1.9 Standard variable overhead rate per direct labor hour $9.00 Actual activity for October Actual variable overhead costs incurred $159,600 Actual direct labor hours 11,400 Actual rotors machined 3,500 What is the variable manufacturing overhead rate variance in October? O A. $42,750 favorable OB. $42,750 unfavorable OC. $57,000 favorable OD. $57,000 unfavorable