Masses of two isobars 29Cu64 and 30Zn64 are 63.9298 u and 63.9292 u. It can be concluded from this
(1) Both isobars are stable
(2) Zn64 is radioactive decaying to Cu64 through β decay
(3) Cu64 is radioactive decaying to Zn64 through γ decay
(4) Cu64 is radioactive decaying to Zn64 through β decay