17. Python has a set type that efficiently implements mathematical sets. You can get information on this container class by consulting reference documents or typing help(set) at a Python prompt. Suppose you are implement-ing your own Set class that includes add, remove, clear, __contains__, intersection, union, and difference operations. Utilizing each of the following concrete data structures, explain how you would implement the required operations and provide an analysis of the run-time efficiency of each operation.

(a) an unordered Python list. (b) a sorted Python list.

(c) a Python dictionary. (Note: the elements of the set will be the keys, you can just use None or True as the value.)