Suppose a Ra 88226 nucleus at rest and in ground state undergoes α...

Suppose a $Ra 88226$ nucleus at rest and in ground state undergoes $\alpha$ -decay to a $Rn 86222$ nucleus in its excited state. The kinetic energy of the emitted $\alpha$ particle is found to be $4.44MeV . Rn 86222$ nucleus then goes to its ground state by $\gamma$ -decay. The energy of the emitted $\gamma$ -photon is _______ $keV,$
[Given: atomic mass of ${}_{88}^{226}Ra = 226.005u,$ atomic mass of ${}_{86}^{222}Rn = 222.000u,$ atomic mass of $\alpha$ particle $= 4.000u, 1u = 931MeV / {c}^{2},c$ is speed of the light]