.(a) Make a list of all the injective mapsShow that none is bijective. (This constitutes a...

.(a) Make a list of all the injective maps

Show that none is bijective. (This constitutes a direct proof that a set A of cardinality three does not have cardinality four.)

(b) How many injective maps

are there? (You can see why one would not wish to try to prove directly that there is no bijective correspondence between these sets.)