Russo Corporation manufactured 17,000 air conditioners during November. The overhead cost-allocation base is $34.75 per machine-hour. The following variable overhead data pertain to November: Actual 17,000 units Production Machine-hours Variable overhead cost per machine-hour: Budgeted 20,000 units 14.000 hours $34.75 12,925 hours $34,00 a) Actual variable overhead cost b) Flexible-budget amount cl Variable overhead spending variance d) Variable overhead efficiency variance