That (1) the only long-run adjustments are caused by the entry and exit of firms, (2) all firms in the industry have identical cost curves, and (3) the industry is constant cost, are all assumptions made to Blank______. Multiple choice question. prove all firms make a normal profit in the short run simplify the examination of profit maximizing perfectly competitive firms in the short run prove all firms make a normal profit in the long run simplify the examination of profit maximizing perfectly competitive firms in the long run