As the nucleus is massive, recoil momentum of the atom may be neglected and the entire energy of the transition may be considered transferred to the Auger electron. As there is a single valence electron in Cr, the energy states may be thought of as given by the Bohr model.
The energy of the nth state En=-Z2R1/n2 where R is the Rydberg constant and Z = 24.
The energy released in a transition from 2 to 1 is
The energy required to eject a n = 4 electron is E4=Z2R 1/16.
Thus the kinetic energy of the Auger electron is