Answer to Question lec33C-1
Other modules are only allowed to use features that are
part of the interface. All of those features are part
of both modules, and, as far as any other module is able
to tell, they have exactly the same effect. For example,
if you insert 1 and 2 into a queue and then remove the first
value, you will get 1, and the queue will only hold
2, regardless of which queue module is used.