Courington Detailing's cost formula for its materials and supplies is $2,070 per month plus $13 per vehicle. For the month of August, the company planned for activity of 87 vehicles, but the actual level of activity was 47 vehicles. The actual materials and supplies for the month was $2,430. The activity variance for materials and supplies in August would be closest to: Multiple Choice $771 F $520 F $520 U $771 U