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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 1.7 Standard variable overhead rate per direct labor hour $10.25 Actual activity for October: Actual variable overhead costs incurred $148,200 Actual direct labor hours 11,400 Actual rotors machined 4,300 What is the variable manufacturing overhead efficiency variance in October? O A. $41,923 favorable OB. $31,350 unfavorable OC. $31,350 favorable OD. $41,923 unfavorable