iv. Add the order_price() function for showing the price of the selected products and the calculated tax in the appropriate text boxes. function order_price () { // get the selected index and the selected item // of "product" var index = . var item_value = // get the quantity ordered var qty ordered = . // if selected index of "product" is 0, disable the // radio buttons "shipping" and reset the form // otherwise enable all the radio buttons "shipping" } // update the total price