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Harris Enterprises machines heavy - duty brake rotors that are used on commercial airliners. The company's management developed the following standard costs: Standard direct labor hours per rotor 1.8 Standard overhead rate per direct labor hour $13.75 Actual activity for October: Actual overhead costs incurred $172.500 Actual direct labor hours 11.500 Actual rotors machined 3.500 What is the variable manufacturing overhead efficiency variance in October? O A. $14,375 favorable O B. $71,500 unfavorable O C. $14,375 unfavorable O D. $71,500 favorable