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

Standard hours per unit of output	2.7 hours
Standard variable overhead rate	$ 13.05 per hour

The following data pertain to operations for the last month:

Actual hours	2,400 hours
Actual total variable manufacturing overhead cost	$ 30,360
Actual output	600 units

What is the variable overhead efficiency variance for the month?

$648 U

$9,867 U

$9,219 U

$10,179 U