i need to insert one value in the first input and auto calculate in the second and third input

2. <input type="text" name="markup" id="markup">
3. <input type="text" name="mark" id="mark">
4. <input type="text" name="marknet" id="marknet">
5. 
   
6. <script type="text/javascript" src="js/jquery.js"></script>
7. <script type="text/javascript">
8. $(document).ready(function(){
10. var item1=$("#markup").val() / 100 ;
11. var item2=$("#mark").val();
12. var item3=item1 * item2;
13. var item4=item3 + item2;
14. $("#markup").change(function(){
15. $("#mark").val(item3);
16. $("$marknet").val(item4);
17. });
18. });
19. </script>
20.