arrSelect=getElementsByClassName("text","select",document.getElementById("shopping_cart"));
arrCost=getElementsByClassName("cost","span",document.getElementById("shopping_cart"));
for(select in arrSelect){
	arrSelect[select].onchange=function(){
		xID=this.id.split('quantity')[1]; 
		xPrice=parseInt(document.getElementById('price'+xID).innerText,10); 
		document.getElementById('cost'+xID).innerText=xPrice*(this.selectedIndex+1)+'.00';
		priceSumm();
	}
}
totalPrice=document.getElementById("totalprice");
function priceSumm(){
	price=0;
	for(cost in arrCost)
		price+=parseInt(arrCost[cost].innerText,10);
	totalPrice.innerText=price+'.00';
}