The Porter Company applies variable manufacturing overhead to its products on the basis of standard direct labor hours. The Porter Company's direct labor efficiency variance was unfavorable for the past quarter. What do we know about the company's variable overhead efficiency variance for the same quarter? A. The company's variable overhead efficiency variance was favorable B. The company's variable overhead efficiency variance was unfavorable C. The company's variable overhead efficiency variance was zero. D. We learn nothing about the company's variable overhead efficiency variance