Answer: a downward sloping supply curve in the long run
Explanation:
In a DECREASING COST industry, producing more output leads to a reduction in costs associated.
Graphically represented then, in the long run when output have Increased, the supply curve will be DOWNWARD sloping as it costs LESS to make MORE.
I have attached a graph to explain further.
As you see, more output means less price so the Supply Curve is sloping downward.
