Answer:
Price will fall , demand curve shift downward , some firms exit
Explanation:
This is a case of perfectly competitive firms - who have same products, same prices, no supernormal profits or abnormal losses.
From a long run equilibrium of normal profits, if there is decrease in industry demand : The firms' identical demand would also decrease, downward sloping demand curve would shift leftwards / downwards. Decreased demand would reduce the over all price in the industry. So, firms will start incurring losses. Hence, many firms will exit the industry. Firms exit would decrease market supply.
Decreased supply would increase market price. Profit would increase at higher price & short run loss (due to demand decrease) would disappear, industry would resume again long run normal profit equilibrium.
