H&X Co. uses a standard job cost system with a normal capacity of 25,400 direct labour hours. H&X Co. produces 12,200 units, which cost $161,000 for direct labour (23,000 hours), $27,938 for variable overhead, and $135,420 for fixed overhead. The standard variable overhead per unit is $2 (2 hours at $1 per hour), and the standard fixed overhead per unit is $10.40 (2 hours at $5.20 per hour).

Calculate the variable overhead spending variance and the variable overhead efficiency variance.

I don't know the formula for variable overhead efficiency variance.