on in this equation and for now a building intuition will make this a lot more formal very soon so let's take a look at another example so think back to think back to our binary trees to encode some set of symbols we have symbol a b c and d if these are the probabilities 1/2 1/4 1/8 1/8 then this thing over here is a optimal way of encoding that have the time you sent just one bit for a the other half of the time you got to cover the rest and to say that you're covering the rest you have to send the one then