Bonjour!
I am going to help clear any confusion you have:
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There are 4 things that Bahais must do everyday:
1 Read from holy writings in the morning
2 Read from holy writings in the evening
3 Repeat "Allahuabha" 95 times
4 Say the obligatory prayer
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You are asking about the obligatory prayers
There are 3 obligatory prayers, and you can choose to say any one of them. There is the SHORT, MEDIUM or LONG obligatory prayer
Each obligatory prayer has different requirements
If you choose to say the SHORT obligatory prayer
reason why it is easy: it is short
reason why it might be difficult: you have to say it at noon
If you choose to say the MEDIUM obligatory prayer
(i do not say the medium obligatory prayer, so i can't comment)
If you choose to say the LONG obligatory prayer
reason why it is easy: you can choose to say it whenever you want to during the 24-hour day
reason why it might be difficult: it is long
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i hope this helps