Marvel Parts, Inc., manufactures auto accessories. One of the company’s products is a set of seat covers that can be adjusted to fit nearly any small car. The company has a standard cost system in use for all of its products. According to the standards that have been set for the seat covers, the factory should work 980 hours each month to produce 1,960 sets of covers. The standard costs associated with this level of production are: Total Per Set of Covers Direct materials $ 32,340 $ 16.50 Direct labor $ 6,860 3.50 Variable manufacturing overhead (based on direct labor-hours) $ 1,960 1.00 $ 21.00 During August, the factory worked only 1,000 direct labor-hours and produced 2,100 sets of covers. The following actual costs were recorded during the month: Total Per Set of Covers Direct materials (6,000 yards) $ 34,020 $ 16.20 Direct labor $ 7,770 3.70 Variable manufacturing overhead $ 3,990 1.90 $ 21.80 At standard, each set of covers should require 2.5 yards of material. All of the materials purchased during the month were used in production. Compute the variable overhead efficiency variance for August?