Dubberly Corporation's cost formula for its manufacturing overhead is $31,700 per month plus $54 per machine-hour. For the month of March, the company planned for activity of 8,120 machine-hours, but the actual level of activity was 7,990 machine-hours. The actual manufacturing overhead for the month was $493,910. The activity variance for manufacturing overhead in March would be closest to: Multiple Choice $23,730 F $7,020 F $23,730 U $7,020 U