给定一段英文文本，将其中的所有英文字母转换为小写，并删除其中的所有标点符号和数字。
Harry Potter and the Philosopher's Stone is a fantasy novel written by British author J.K. Rowling. The story follows young Harry Potter, who discovers on his eleventh birthday that he is a wizard.
harry potter and the philosopher s stone is a fantasy novel written by british author j k rowling the story follows young harry potter who discovers on his eleventh birthday that he is a wizard