Courington Detailing's cost formula for its materials and supplies is $1,980 per month plus $10 per vehicle. For the month of August, the company planned for activity of 93 vehicles, but the actual level of activity was 53 vehicles. The actual materials and supplies for the month was $2,820. The activity variance for materials and supplies in August would be closest to: Multiple Choice $90 F $90 U $400 F $400 U