Rupert Murdoch ,the founder of News Corp.  Tweeted yesterday that Apple shares at the $448 level are resoundingly cheap if the Facebook  public offering values the whole of Facebook at $75-$100 billion. Murdoch’s amazing decision to plug another company  must be a first for Murdoch or any other media and entertainment bigwig. It comes just after JP Morgan issued a hugely bullish recommendation on Apple shares, predicting they will sell…