The functions are .

To find .

             (Substitute g(5) = 4)

                 (Substitute g(8) = 3)

                            (Substitute g(2) = 2)               

has no element  in the function g, so not exist.

To find .

            (Substitute f(2) = 5)

                        (Substitute  f(3) = 9)

                     (Substitute  f(4) = 1)

has no elements  in the function f, so not exist.

and not exist.