[Robk]

Expected chip count if you fold = 20000*.6 = 12000

Expected chip count if you call = 15000*p + 5000*(1-p) = 10000p + 5000 = 12000
=>10000p = 7000 => p = .7

I don't recall ever getting one of these right, but I'm going to keep trying. There's a first time for everything.