Help Again please

I'm having issues with getting everything to total up right. Any suggestions would help. It's only multiplying the last price by the last amount. Thanks. Nathan M

<SCRIPT LANGUAGE = "JavaScript"> /* This code takes input from user, adds it all up and gives a total at the bottom

         * of all the products for seven days and the corresponding value of them all */





  var retail_price, validInput = true, counter = 1, total = 0, amount_sold = 0, total_retail_value = 0;



  while (counter < 8) {

  pro_num = window.prompt ("Enter a product number (1-5)", "0");

  

  

  

  

  switch (pro_num) {

   case "1":

    price = 2.98;

    break;

   case "2":

    price = 4.50;

    break;

   case "3":

    price = 9.98;

    break;

   case "4":

    price = 4.49;

    break;

   case "5":

    price = 6.87;

    break;

   default:

    validInput = false;

   }

  if ( validInput == true) {

    amount_sold = window.prompt("Enter number of products sold", "0");}

    counter++;

  }

  



    document.writeln("Total Retail Value of all products sold over 7 days equals: " + ( amount_sold * price));

  



  









</SCRIPT>