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# Masses of two isobars $\;_{29}^{64}Cu\;$ and $\;_{30}^{64}Zn\;$ are 63.9298n and 63.9292n respectively.It can be concluded from these data that

$(a)\;both\;the\;isobars\;are\;stable\qquad(b)\;^{64}Zn\;is\;radioaingctive\;,decaying\;to\;^{64}Cu\;through\;\beta-decay\qquad(c)\;^{64}Cu\;is\;radioactive\;,decaying\;to\;^{64}Zn\;through\;y-decay\qquad(d)\;^{64}Cu\;is\;radioactive\;,decaying\;to\;^{64}Zn\;through\;\beta-decay$

Answer : $\;^{64}Cu\;is\;radioactive\;,decaying\;to\;^{64}Zn\;through\;\beta-decay$
Explanation :
The atomic mass of Cu is expected to be a smaller than Zn . Since the given mass is larger , it is expected to be unstable. In $\;beta-\;$ decay , atomic number is increased by one while mass number remains the same.