Manahoana, Manakory and Akory: How are they different?

When you look at Malagasy phrase books you will see these three words:
Manahoana
Manakory
Akory
They are listed with the following meanings:
Hello
How are you?
Good morning!
Good afternoon!
Good evening!
I understand languages where there are catchall greeting terms like Aloha in Hawaiian or chào in Vietnamese so that is not necessarily an issue with me. But to avoid confusion and also I would like to know the exact meaning of each word, how they are different are there any cases you would use one and not the other?
Thanks!