(a)If you are given an interface for an ADT, but not an actual source file, how well can you program against it?

(Hint: there is a type of methods that cannot be specified in an interface)

(b) when it comes to performance(not funtionality) is it important to know how an ADT is internally implemented?

(c) would it be safer(more secure/reliable) to expose an mutable or immutable type to an unknown 3rd party library? explain