Help!! Interpreting Energy-Level Diagrams!!?

spectral lines are obtained when electron makes a transition from a higher energy level to a lower one thereby releasing energy in the form of photons. let us ume that electron is in E5. so it can make single transition to E4, E3... and lower levels. thus a maximum of (n-1) transitions are possible where n is maximum energy level with each transition corresponding to a spectral emmision. the maximum level to which electron jumps can be found out using ionisation potential of mercury atom.