Ch. 9 - Kovac Snow Removal's cost formula for its vehicle operating cost is $2900 per month plus $320 per snow-day. For the month of December, the company planned for activity of 15 snow-days, but the actual level of activity was 13 snow- days. The actual vehicle operating cost for the month was $7980. The spending variance for vehicle operating cost in December would be closest to: $280 F $280 U $280 U $280 F