Why a capital E for Est, a small o for ouest and a capital S for Atlantique Sud, please?

Hi Eleanor,

Good question! 

We are actually accepting both capitals and no capitals on the cardinal points used in this exercise, hence the discrepancy you are noting.

However, the rules are that you would use capitals when the cardinal points are used to describe a geographical unit.

This is what the Académie says about Nord which you might find interesting -

https://www.dictionnaire-academie.fr/article/A9N0648

Hope this helps!