here thank you yes so in this case we haven't gotten to the mixture yet where we're gonna talk about that soon this is just for this very simple source over here it's just a coin flip but we just want to store coin flips there's no latent variables or anything like that the second question was where does the stack come in it comes in the fact that so let's say we but let's say we encode a sequence of symbols say B a B and so that's if we follow this encoding rule then that's gonna produce a sequence of states it's gonna be like s1 s2 s3 and