Assume the following code: LinkedList I$=$new LinkedList$()$; l$.$add$(4)$;

l$.$add$(1,5)$;

l$.$add$(2,1)$;

l$.$add$(3,2)$;

l$.$add$(1,3)$;

l$.$peekFirst$()$;

What does I.peekFirst$()$ return?