Miguez corporation makes a product with the following standard costs: standard quantity or hours standard price or rate standard cost per unit direct materials 2.3 liters $ 7.00 per liter $ 16.10 direct labor 0.7 hours $ 22.00 per hour $ 15.40 variable overhead 0.7 hours $ 2.00 per hour $ 1.40 the company budgeted for production of 2,600 units in september, but actual production was 2,500 units. the company used 5,440 liters of direct material and 1,680 direct labor-hours to produce this output. the company purchased 5,800 liters of the direct material at $7.20 per liter. the actual direct labor rate was $24.10 per hour and the actual variable overhead rate was $1.90 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 efficiency variance for september is:

a. $140 u

b. $140 f

c. $133 f

d: $133 u