How do I fade .addClass in and out.

Here is the link -

www.aus-media.com/dev/site_BYJ/new-students/

and here is the code -

$(document).ready(function() {
  $('#menu li#Q_01,#menu li#Q_03,#menu li#Q_05,#menu li#Q_07,#menu li#Q_09,#menu li#Q_11,#menu li#Q_13').hover(function() {
    $(this).addClass('pretty-hover');
  }, function() {
    $(this).removeClass('pretty-hover');
  });
});

$(document).ready(function() {
  $('#menu li#Q_02,#menu li#Q_04,#menu li#Q_06,#menu li#Q_08,#menu li#Q_10,#menu li#Q_12').hover(function() {
    $(this).addClass('pretty-hover_01');
  }, function() {
    $(this).removeClass('pretty-hover_01');
  });
});

Thanks