There are two stacks of cards. The first stack consists of 5 red cards and 5 black cards, and the second stack consists of 10 red cards.

There are two stacks of cards. The first stack consists of 5 red cards and 5 black cards, and the second stack consists of 10 red cards. One of the stacks is picked at random, and from it 3 cards are chosen at random without replacement. The 3 cards are found to be red. Having this information revealed to you, what is the probability that the first stack was selected?