Dubberly Corporation's cost formula for its manufacturing overhead is $31,500 per month plus $58 per machine-hour. For the month of March, the company planned for activity of 8,080 machine-hours, but the actual level of activity was 7,970 machine-hours. The actual manufacturing overhead for the month was $523,630. The activity variance for manufacturing overhead In March would be closest to: Multiple Choice $23.490 U O $23.490 F O $6.380 F O $6,380 U