Haskell Monads - Monad do syntax

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