Assume the variable overhead standard is 5 machine hours at $7 per hour and the fixed overhead standard is 5 machine hours at $9 per hour based on a planned activity of 35,000 machine hours when 7,000 units were scheduled to be produced. Given the following data: Actual variable overhead incurred: $254,750 Actual fixed overhead incurred: $375,000 Actual machine hours used: 34,800 Actual units produced: 7,100 the variable overhead efficiency variance is: Multiple Choice O $640 favorable. O $640 unfavorable. O $4,900 favorable O $4,900 unfavorable. O None of the answers is correct