Total de horas da fatura do Freshbooks

https://gist.github.com/3910293

$('.invbody-items:first tbody tr').map(function(){
  return parseInt($(this).find('td:eq(3)').text().trim(), 10);
 }).get().reduce(function(left, right){
  return (left || 0) + (right || 0);
});  // total hours as a number