We report a study of B J=c K and B c K decay modes using 772 10 B B events
collected at the 4S resonance with the Belle detector at the KEKB energy-asymmetric eecollider.
We observe X3872 J=c and report the first evidence for
J=c in B
decays, while in a search for X3872 c significant signal is found. We measure the branching