Xcel Technologies, Inc. applies variable manufacturing overhead to products based on machine hours. The standard variable overhead rate is $5 per machine hour. The standard time allowed for producing one unit is 2 machine hours. During the month of August, the company produced 500 units. It incurred actual variable costs of $5,655 and used 870 machine hours. Calculate the variable overhead efficiency variance for the month of August.

A) $650 favorable

B) $650 unfavorable

C) $845 favorable

D) $845 unfavorable