Why does driver 3 most likely pay a higher monthly premium than drivers 1 and 2

Doogan corporation makes a product with the following standard costs: standard quantity or hours standard price or rate direct materials 2.0 grams $ 7.00 per gram direct labor 1.6 hours $ 12.00 per hour variable overhead 1.6 hours $ 6.00 per hour the company produced 5,000 units in january using 10,340 grams of direct material and 2,320 direct labor-hours. during the month, the company purchased 10,910 grams of the direct material at $7.30 per gram. the actual direct labor rate was $12.85 per hour and the actual variable overhead rate was $5.80 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 materials quantity variance for january is: