Add a quadruple function. (Maybe it could call the double function...)
See the Times.exs file.
We added the function definition:
def quadruple(n), do: n |> double |> double
It calls double for the sake of using another function within the module; however, realistically it would be simpler to define it as:
def quadruple(n), do: n * 4
Let's run it:
iex> Times.quadruple 5
20