The mass of a nucleus ${ }_Z^A X$ is less that the sum of the masses of $(A-Z)$ number of neutrons and $Z$ number of protons in the nucleus. The energy equivalent to the corresponding mass difference is known as the binding energy of the nucleus. A heavy nucleus of mass $M$ can break into two light nuclei of masses $m_1$ and $m_2$ only if $\left(m_1+m_2\right)<M$. Also two light nuclei of masses $m_3$ and $m_4$ can undergo complete fusion and form a heavy nucleus of mass $M^{\prime}$ only if $\left(m_3+m_4\right)>M^{\prime}$. The masses of some neutral atoms are given in the table below : The kinetic energy (in keV ) of the alpha particle, when the nucleus ${ }_{84}^{210} \mathrm{P}_0$ at rest undergoes alpha decay, is: