For the transitions described in the previous exercise, is there any relationship among the wavelengths of the

Question:

For the transitions described in the previous exercise, is there any relationship among the wavelengths of the emitted photons?
Previous exercise
An electron de-excites from the fourth quantum level in the diagram of Exercise 52 to the third and then directly to the ground state. Two photons are emitted. How does the sum of their frequencies compare with the frequency of the single photon that would be emitted by de-excitation from the fourth level directly to the ground state?