Assume that the cost formula for one of a company's mixed expenses is $10,000+ $4.00 per unit. The company's planned level of activity was 2,000 units and its actual level of activity was 2,200 units. The actual amount of this expense was $18,120. The spending variance for this expense is: Multiple Choice O $680 F. $1,680 U. O O O $280 U. O O $1,680 F