Martin Company, which applies overhead to production on the basis of machine hours, reported the following data for the period just ended: Actual units produced: 9,000 Actual variable overhead incurred: $54,400 Actual machine hours worked: 16,000 Standard variable overhead cost per machine hour: $3.50 If Martin estimates two hours to manufacture a completed unit, the company's variable-overhead efficiency variance is: $1,600 favorable. $1,600 unfavorable. $7,000 favorable. $7,000 unfavorable. some other amount not listed above.