The isotope `_(5)^(12) B` having a mass `12.014 u`undergoes beta - decay to `_(6)^(12) C _(6)^(12) C `has an excited state of the nucleus `( _(6)^(12) C ^(**) at 4.041 MeV` above its ground state if `_(5)^(12)E` decay to `_(6)^(12) C ^(**) ` , the maximum kinetic energy of the `beta` - particle in unit of MeV is `(1 u = 931.5MeV//c^(2)` where c is the speed of light in vaccuum) .

Explanation

Q value `=[12.014u-(12u+4.041(MeV)/(c^(2)))]c^(2)`
`Q=(0.014uxx931.5)MeV-(4.041)MeV=9 MeV`
Hence, `beta` particle will have a maximum KE of `9 MeV`.