Dark Ascension booster pack contents?

[Bort]

Does anyone know the exact probability of getting a mythic rare instead of a regular rare?

I just opened a couple booster packs for Dark Ascension in real life and it seems like it contains 14 cards, plus a token. It appears that a pack always contains exactly one 2-sided card. There are 9 commons, 3 uncommons, a rare (or mythic rare), and also a 2-sided card. I know the rarity of the 2-sided card is random.

Does anyone know the probabilities of the 2-sided card being a rare, mythic, common, or uncommon?

If I know the exact probabilities I can better simulate virtual packs.