Hello Alaska, indeed this question is a tricky one! And I assume there is a spelling error with the names.

A common mistake that students do is to add all the days together, such that: 2 Johns 2 Raufs, 2 Deans will take 13 days to complete the train, etc. This concept is incorrect.

When working on questions related to "Rates", we will have to ensure that the numbers are compared with the same units. This is the reason why we have to find out how much of the train is completed in a day.

I hope this solution finds you well! If you have any doubts or require any clarification, do feel free to contact me :)