A bag can contain more than one copy of an item. For example, the chapter describes a bag that contains the number 4 and two cop ies of the number 8. This bag behavior is different from a set, which can contain only a single copy of any given item. Write a new container class called set, which is similar to a bag, except that a set can contain only one copy of any given item. You'll need to change the interface a bit. For example, in- stead of the bag's count function, you'll want a con- stant member function such as this: bool set contains (const value type& target) const; Postcondition: The return value is true if target is in the set, otherwise the return value is false. Make an explicit statement ofthe invariant of the set class. Do a time analysis for each operation. At this