I'm having trouble figuring out how to do this problem, when I work through it I keep getting the wrong answer: the hydrogen atom emission spectrum...

I'm having trouble figuring out how to do this problem, when I work through it I keep getting the wrong answer: the hydrogen atom emission spectrum contains a spectral line at 410nm. Using the Rydberg equation, determine the principal quantum number (n) of the level from which the electron falls as it returns to the n=2 level.