Need help with understanding this

1pt] Data Structures 1: On the right is a series of operations performed on a data structure. What will be the contents of the data structure after the given sequence if the data structure is (a) stack, or (b) a queue? Note peek () looks at the next thing that will be removed (without removing it). Structure s= new structure (); s.add (3); s.add (9); if (s.peek ()>4) s.remove (); s.add (2); s.add (7); s.remove ()