The conversation between human and AI assistant.
[|Human|] Given this reference text, how old was Trey Anastasio when he co-founded Phish?
[|AI|] Based on this passage, Trey was most likely 19 years old. He was born at the end of September in 1964 so there is a 25% chance that he was 20 years old when he co-founded Phish.
[|Human|] 
Given this reference text, how old was Trey Anastasio when he co-founded Phish?