An atom of a certain element absorbs light with its wavelength of 520nm while passing from its second to its fifth energetic level. The atom absorbs a foton with a wavelength while passing from the second to the sixth energy level.
a) Find the energy that would be absorbed if it passed from its fifth to its sixth energetic level
b)Explain what would happen if the transition was from sixth to fifth energetic level

I need to understand how this works, I want an explanation please.