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

Standard hours per unit of output	7.6	hours
Standard variable overhead rate	$14.00	per hour

The following data pertain to operations for the last month:

Actual hours	2,800	hours
Actual total variable manufacturing overhead cost	$39,910
Actual output	150	units

What is the variable overhead efficiency variance for the month?

$23,240 U

$23,950 U

$15,960 F

$710 F