Your friend takes a coin out of his pocket and tosses it three times. You know that he had a two-headed coin and a regular coin in is pocket, and you believe that it is equally likely for him to have...

Your friend takes a coin out of his pocket and tosses it three times. You know that he had a two-headed coin and a regular coin in is pocket, and you believe that it is equally likely for him to have chosen either coin. The outcome of the tosses comes up heads, heads, heads. What is the chance that your friend originally chose the two-headed coin?