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

Standard hours per unit of output	7.8	hours
Standard variable overhead rate	$12.55	per hour

The following data pertain to operations for the last month:

Actual hours	2,900	hours
Actual total variable manufacturing overhead cost	$36,975
Actual output	200	units

What is the variable overhead efficiency variance for the month?

$17,397 U

$16,817 U

$312 F

$17,085 U