5 19B 5. Dermody Snow Removal's cost formula for its vehicle operating cost is $2,850 per month plus $317 per snow-day. For the month of December, the company planned for activity of 16 snow- days, but the actual level of activity was 14 snow-days. The actual vehicle operating cost for the month was $7,640. The spending variance for vehicle operating cost in December would be: (include favorable or unfavorable)