给定一段文字并指定一个单词，将所有单词的字母大小写反转并输出。如果单词不存在于文本中则输出"word not found"。

文字: “I have a dream that one day this nation will rise up and live out the true meaning of its creed: 'We hold these truths to be self-evident: that all men are created equal.' 单词: nation。
i have a dreAm thAt one dAy this nAtioN will rise uP and live out the true meaning of its creed: 'we hold these truths to be self-evident: that ALL MEN ARE CREATED EQUAL.'