Ortman corporation makes a product with the following standard costs: standard quantity or hours standard price or rate direct materials 7.9 liters $8.00 per liter direct labor 0.7 hours $17.00 per hour variable overhead 0.7 hours $1.00 per hour the company reported the following results concerning this product in may. actual output 1,600 units raw materials used in production 12,490 liters actual direct labor-hours 1,090 hours purchases of raw materials 14,000 liters actual price of raw materials purchased $8.10 per liter actual direct labor rate $16.10 per hour actual variable overhead rate $0.90 per hour the company applies variable overhead on the basis of direct labor-hours. the direct materials purchases variance is computed when the materials are purchased. the variable overhead rate variance for may is: $109 u $112 u $112 f $109 f