# Question: let x 1 2 3 4 and y ...

###### Question details

Let X = {1, 2, 3, 4} and Y = {a, b, c, d, e}. Write down examples of functions

following properties:

(a) g ∶ X → X so that g is injective and surjective.

(b) h ∶ X → Y so that h is injective but not surjective. (c) i ∶ Y
→ X so that i is surjective but not injective.

(d) j ∶ X → Y so that j is neither surjective nor injective.

with the

Can you find an example of a map k ∶ N → N that is not surjective? Prove your answer.