Why is pure competition considered an unsustainable system?

The reason why pure competition is considered an unsustainable system because with pure competition, both sellers and buyers would not be able to control or manipulate the market. It would be difficult for the buyers to keep up if the prices are high and they cannot afford and sellers have the choice to either stay in the price or lower it down.

1190 is your answer! the way you get it is 1400 - 15% =1190 : )