function updatePrice(price)
{
  persons = document.getElementById('persons').value;
  if (isNumeric(persons) && persons != '0')
  {
    total = ((price * persons) / 100);
    formatted_price = total.toFixed(2)
    formatted_price = formatted_price.replace('.',',');
    document.getElementById('price').innerHTML = formatted_price;
  }
  else if (persons == '0')
  {
    total = price/100;
    formatted_price = total.toFixed(2)
    formatted_price = formatted_price.replace('.',',');
    document.getElementById('price').innerHTML = formatted_price;
    document.getElementById('persons').value = '1';
  }
  else
  {
    alert("U hebt geen numerieke waarde ingevuld");
    total = price/100;
    formatted_price = total.toFixed(2)
    formatted_price = formatted_price.replace('.',',');
    document.getElementById('price').innerHTML = formatted_price;
    document.getElementById('persons').value = '1';
    return false;
  }
  return true;
}

function isNumeric(persons)
{
   if ((isNaN(persons)) || (persons.length == 0)) return false;
   return true;
}