we stand i same cost as before using encoding based on the prior like the I why not P I give an X you might say isn't that more peak can we just send P are given X well the recipient doesn't have X so they cannot decode it against a given X they have nothing else we send I is the first thing we say well they have to decode a dist on the prior and you have to encode it based enough then we send backs using same encoding scheme as before this is probably efficient but not necessarily as efficient as using the best I remember imagine we have