9. Prove that if A and B are
finite sets with |A| =
|B|, then any injection f :
A → B is
also a surjection. Show this is not necessarily true if
A and B are not finite.
10. Prove that if A and B are
finite sets with |A| =
|B|, then any surjection f :
A → B
is also an injection. Show this is not necessarily true if
A and B are not finite