Ravena Labs., Inc. makes a single product which has the following standards: Direct Materials 2.5 ounces at $20 per ounce Direct Labor 1.4 hours at $12.50 per hour Variable Manufacturing Overhead 1.4 hours at ? per hour Variable manufacturing overhead is applied on the basis of direct labor hours. The following data are available for October: 3750 units of compound were produced during the month. There was no beginning direct materials inventory The ending direct materials inventory was 2000 ounces Direct materials purchased: 12000 ounces for $225,000 Direct labor hours worked: 5600 hours at a cost of $67,200 Variable manufacturing overhead costs incurred amounted to $18200 Variable manufacturing overhead applied to products: $18,375 The variable overhead efficiency variance for October is