问题描述：
英语翻译
when strong economy of scale and learning effects are present since it takes time to obtain the volume and learning to yield a low relative cost per unit,if firms already present are vertically integrated,entry becomes even more expensive.also,if the existing firms share their output with their related businesses,the problem of overcoming the cost disadvantage is made even more difficult.
when strong economy of scale and learning effects are present since it takes time to obtain the volume and learning to yield a low relative cost per unit,if firms already present are vertically integrated,entry becomes even more expensive.also,if the existing firms share their output with their related businesses,the problem of overcoming the cost disadvantage is made even more difficult.
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