function calculPrice(id, pricepercut, price)
{
  var size = document.getElementById(id).size.value.replace(",",".");
  var unit = document.getElementById(id).unit.value.replace(",",".");
  var finalPrice = price*size*unit + unit*pricepercut;
  var waitFinalPrice = Math.round (finalPrice*100);
  finalPrice =  waitFinalPrice/100;
  document.getElementById(id).price.value = finalPrice;
}