Haskell Monads - The Either Monad

This topic is for the [The Either Monad] exercise in the [Haskell Monads] trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.
[The Either Monad]: https://exercises.upcase.com/exercises/the-either-monad
[Haskell Monads]: Haskell Monads | Online Tutorial by thoughtbot