Answer:
26 keV
Explanation:
The electron is being ejected from the L -shell which has a binding energy of 26 keV.
Now the electron is being added to fill the vacancy in the L shell. Since, the binding the energy of the electron for the L-shell is 26 keV, so the energy produced is also equal to this amount of energy.
So, the characteristic x-ray produced will have an energy of 26 keV.