Admac Technologies has a standard variable overhead rate of $5.40 per machine hour, and each unit produced has a standard time allowed of 2.60 hours. The company's static budget was based on 46,000 units. Actual results for the year follow. Actual units produced: 40,000 Actual machine hours worked: 100,000 Actual variable overhead incurred: $520,000 Admac's variable-overhead efficiency variance is: Multiple Choice $20,000 favorable. O $20,000 unfavorable. O $21,600 favorable. O $21,600 unfavorable