Excited vs. Ground state masses of atom

[danok]

1. In a certain gamma decay process, an excited neon atom emits a gamma-ray that has an energy of 1.630 MeV. The neon atom in the ground state has a mass of 19.992 435 u. What is the mass of the excited neon atom?



2. I am pretty lost here. There must be a formula relating these energies to masses somewhere, but I do not know it.

 

[kuruman]

Try E = mc².