The company budgeted for production of 2,400 units in June, but actual production was 2,500 units. The company used 19,850 pounds of direct material and 980 direct labor-hours to produce this output. The company purchased 21,700 pounds of the direct material at $6.70 per pound. The actual direct labor rate was $19.20 per hour and the actual variable overhead rate was $1.80 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 variable overhead efficiency variance for June is:

a. $36 U
b. $36 F
c. $40 U
d. $40 F