"a perfectly competitive market. The firm will stay in the market in the long run only if the market price is greater than or equal to"

$10 for 200 units which means $0.05 per unit.

Explanation:

The firm will only survive in a perfectly competitive market if its average cost is at minimum level which we can see in the figure. The lowest average cost is $10 for 200 units which means average cost per unit is $0.05 per unit. At this stage the company will be able to produce higher profits because its average cost per unit is at minimum level.

answer; (d) i believe that the correct answer is ; /// a new invention lowers the cost of production;