5. Let X, Y and Z be sets. Let f : X ! Y and g : Y ! Z
functions.
(a) (3 Pts.) Show that if g f is an injective function, then f
is an injective function.
(b) (2 Pts.) Find examples of sets X, Y and Z and functions f
: X ! Y and g : Y ! Z such that g f is
injective but g is not injective.
(c) (3 Pts.) Show that if...