The following standards for variable manufacturing overhead have been established for a company that makes only one product:

Standard hours per unit of output	7.2	hours
Standard variable overhead rate	$13.60	per hour

The following data pertain to operations for the last month:

Actual hours	2,750	hours
Actual total variable manufacturing overhead cost	$38,090
Actual output	250	units

What is the variable overhead efficiency variance for the month?

$690 F

$12,920 U

$13,610 U

$24,480 F