What is the daughter nucleus (nuclide) produced when 64cu undergoes beta decay by emitting an electron? replace each question mark with the appropriate integer or symbol?

Answer is: daughter nucleus is zinc.
Nuclear reaction 3: ⁶⁴Cu → ⁶⁴Zn + e⁻ + electron antineutrino.
Beta decay is radioactive decay in which a beta ray and a neutrino are emitted from an atomic nucleus.
There are two types of beta decay: beta minus and beta plus. 
In beta minus decay, neutron is converted to a proton and an electron and an electron antineutrino and atomic number Z is increased by one.