Q:  What are the wavelengths of the H-beta 
       and H-alpha lines in this galaxy's spectrum?

       What is the shift in wavelength for each line
       from the rest wavelength?

       How fast is this galaxy moving?  In which direction?


      line       rest         galaxy       shift         velocity
   -----------------------------------------------------------------------

    H-alpha      656 nm        721 nm       65 nm      0.1 c = 30,000 km/s

    H-beta       486 nm        535 nm       49 nm      0.1 c = 30,000 km/s

   -----------------------------------------------------------------------

       Because the observed wavelengths are longer than the rest
       wavelengths, the galaxy is moving away from us.

       Notice that even though the shift in nm is different for
       the two lines, the _fractional_ shift

                                 shift in wavelength
           fractional shift  =  ---------------------
                                   rest wavelength

       is the same.