Beyonc is looking at a monthly performance report for her lemonade stand for last month. She has been provided with the following standard cost per batch of lemonade: Cost Standard Quantity (Input per Batch) Standard Price Direct Materials 0.8 pounds $5.00 per pound Direct Labor 1.2 hours $15.00 per hour Standard Costs are based on machine hours. Last month, Beyonc's lemonade stand produced 150 batches of lemonade and incurred the following costs: a. Purchased 100 pounds of materials at a cost of $4.2 per pound. b. Used 87 pounds of materials in production. (Finished goods and work in process inventories can be ignored). c. Worked 162 direct labor-hours at a cost of $16.48 per hour. What is Beyonc's labor efficiency variance for last month?