Zero Company's standard factory overhead rate is $3.75 per direct labor hour (DLH), calculated at 90% capacity = 900 standard DLHs. In December, the company operated at 80% of capacity, or 800 standard DLHs. Budgeted factory overhead at 80% of capacity is $3,150, of which $1,350 is fixed overhead. For December, the actual factory overhead cost was $3,800 for 840 actual DLHs, of which $1,300 was for fixed factory overhead. Assuming the use of a four-way breakdown (decomposition) of the total overhead variance, what is the variable factory overhead efficiency variance for Zero Company in December?

$650 unfavorable.

$150 unfavorable.

$225 favorable.

$425 unfavorable.

$90 unfavorable.