Answer:
All : 1st, 2nd, 3rd are False
Explanation:
1. Average total cost is always greater than average variable cost by a constant amount : False.
Average Total Cost (ATC) is the total cost per unit of output. ATC = Average Variable cost (AVC) + Average fixed cost (AFC). Total fixed cost (TFC) is the cost which stays same at all levels, AFC = TFC / Q falls with increasing output. So, ATC is greater by AVC, by AFC (decreasing) amount.
2. In the short run, a perfectly competitive firm always maximises profit when average total cost is at minimum : False
A perfectly competitive firm maximises profit in short run when difference between its Total Revenue & Total cost is maximum, Marginal Revenue = Marginal Cost & MC > MR after the point.
3. If a firm shuts down in the short run, its profits will equal zero : False
A firm shuts down in short run, when its price < average variable cost, or firm's average revenue < average variable cost. This implies that firm must be incurring losses, if it shuts down.