Dari - estimates put Darie speakers at around 12-15 million mostly clustered in the central asian area of Afghanistan.
French - other than France - it's the official language of the UN and most international organizations. Around 145 million folks in the Euro zone speak French to some degree - and something like 27-29 countries have French as their official language.
Now I ain't sayen' but.............
OK, Dari will be a good work language but when some "Hey You" comes down where they need someone who can speak French...............
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English, Dari and French - sounds like a good combination.