The functions are .

To find .

                       (Substitute g(4) = 5)

                        (Substitute g(2) = 4)

                        (Substitute g(6) = 8)

                   (Substitute g(8) = 10)

.

To find .

                               (Substitute f(4)= 5)

                               (Substitute  f(6)= 5)

                  (Substitute  f(8)= 12)

                          (Substitute  f(10)= 12)

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

  and not exist.