Challenge From Mr. Professor

One Day Mr. Professor was taking His schedule class on Discrete Mathematics. In this lecture, He was talking about set theory. Alice was very lazy and Inattentive in this class. Mr. Professor notices him and thinks How to punish him. After finishing His class Mr. Professor Write Two Function on the blackboard and some description.


This is a companion discussion topic for the original entry at https://toph.co/p/challenge-from-mr-professor