Wilson Corporation has a standard cost system in which it applies manufacturing overhead to products on the basis of standard machine-hours (MHs) at $4.00 per MH. During the month, the actual total variable manufacturing overhead was $18,040 and the actual level of activity for the period was 4,100 MHs. What was the variable overhead rate variance for the month? $1,640 Unfavorable $410 Favorable $410 Unfavorable $1,640 Favorable