Evergreen Corporation has provided the following information relating to their operations: Standard direct labor hours to produce one chair is 4.5 hours. Standard direct labor rate is $70 per hour. For May 2017, Evergreen had budgeted production at 140 units. Direct labor hours to produce the actual output of 155 chairs was 750 hours. The actual cost of the direct labor hours was $50,000. Evergreen's labor efficiency variance for May 2017 was _______.