In the diagram, the energy difference between states A and B is twice the energy difference between

Question:

In the diagram, the energy difference between states A and B is twice the energy difference between states B and C. In a transition (quantum jump) from C to B, an electron emits a photon of wavelength 600 nm.
a. What is the wavelength emitted when the photon jumps from B to A?
b. When it jumps from C to A?