Consider four coins, three of which are fair, that is they have heads on one side and tails on the other and both are equally likely to occur in a toss. The fourth coin has heads on both sides. Given that one coin amongst the four is picked at random and is tossed, and the outcome is seen to be head, what is the probability that its other side is tails?
- $1 / 2$
- $3 / 8$
- $3 / 5$
- $3 / 4$
- $5 / 7$