Radon decays as follows: ${ }^{222} \mathrm{Rn} \rightarrow{ }^{218} \mathrm{Po}+\alpha$. The mass of the radon-222 nucleus is $221.97039 \mathrm{u}$, the mass of the polonium- 218 nucleus is $217.96289 \mathrm{u}$, and the mass of the alpha particle is $4.00151 \mathrm{u}$. How much energy is released in the decay? $\left(1 \mathrm{u}=931.494 \mathrm{MeV} / \mathrm{c}^{2} .\right)$