Using function concepts, it is found that it is increasing on the interval:
(–∞, –5] ∪ [3, ∞)
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The function is given by:

The graph is given at the end of this question.
- If the function is pointing upwards, it is increasing. Otherwise, it is decreasing.
- In the graph, it can be seen that it is pointing upwards for x of -5 and less, or 3 and higher, thus, the interval is:
(–∞, –5] ∪ [3, ∞)
A similar problem is given at brainly.com/question/13539822
When the demand and supply curve intersect, that is, where the quantity demanded and quantity supplied are equal, the market is said to be in equilibrium. Thus, the given quantity is equilibrium quantity.
From the graph, we see that when the production cost of wheat is $4, the equilibrium quantity is 600 units.
When the production cost lowers from $4 to $3, the supply of wheat increases, such that the equilibrium quantity increases from 600 units to 800 units.
Thus, after an increase in supply, the equilibrium quantity increases.
So, Option A is the correct answer.