In the long run Firm A incurs total costs of $1,050 when output is 30 units and $1,200 when output is 40 units. Firm A exhibits:

economies of scale because total cost is rising as output rises.

economies of scale because average total cost is falling as output rises.

diseconomies of scale because total cost is rising as output rises.

diseconomies of scale because average total cost is rising as output rises.