Face Down + Hidden Mana

Just for informational accuracy, in Magic, cards are played face down for 3, not 1, unless you have certain cards in play, but that's not really important in this topic.

Back to the topic, I haven't been paying attension to this so I would like to know, If all the face down cards are revealed, is the mana also revealed at that point. (Show how much me knowing my opponent's mana affects my game.)