Issue with basic shopping cart

Issue with basic shopping cart

Hello folks,
 
I got a little complicated with summing the shoping cart prices.
 
I have this shopping cart:
 
I
 
 
I wrote this function for updating the basic sum:
  1.  function changePrice(divId, sId, price) {
      var x = $("#" + sId).val();
      var y = $("#" + divId).text(x*price + " ₪");
     }



 
and the HTML form something like that:
  1.    <form>
        <select id="selectQuan-1" onChange="changePrice('sum-1','selectQuan-1','678');">
         <option value="0">0</option>
         <option value="1" selected>1</option>
         <option value="2">2</option>
         <option value="3">3</option>
         <option value="4">4</option>
         <option value="5">5</option>
        </select>
       </form>








Now, I'm trying somehow to update the total sum in the div #totalSum. I tried to push the sums of the products into an array.. But I didn't work it out.
 
Can somebody please help me/lead me to the solution?
 
thank you very much.