Gerhan Company's flexible budget for the units actually manufactured in May shows $16,642 of total factory overhead; this output level represents 73.00% of available capacity. During May the company applied overhead to production at the rate of $3.20 per direct labor hour (DLH), based on a denominator volume level of 6,441 DLHs, which represents 93.00% of available capacity. The company spent 5,200 DLHs and incurred $17,410 of total factory overhead cost during May, including $7,180 for fixed factory overhead.
What is the factory overhead efficiency variance for May under the assumption that Gerhan uses a four-variance breakdown (decomposition) of the total overhead variance?