The Maxwell Corporation has a standard costing system in which variable manufacturing overhead is assigned to production on the basis of standard machine-hours. The following data are available for July:

Actual variable manufacturing overhead cost incurred: $26,800

Actual machine-hours worked: 3,500 hours

Variable overhead rate variance: $6,270 Unfavorable

Total variable overhead spending variance: $8,800 Unfavorable

The variable overhead efficiency variance for July is:

a. $2,530 Unfavorable

b. $15,070 Unfavorable

c. $2,530 Favorable

d. $15,070 Favorable