Assume that the cost formula for one of a company$$s variable expenses is $$5\mathrm{.}40$ per unit. The company$$s planned level of activity was $2,000$ units and its actual level of activity was $2,200$ units. The actual amount of this expense was $$10,800.$ The activity variance for this expense is

$$280$ F$.$

$$280$ U$.$

$$1,080$ U$.$

$$880$ U$.$