One set of lines appears at roughly

        Sun:        883.8 nm     
        Arcturus:   884.0 nm     

  which means that the difference is 

         delta_lambda = 884.0 - 883.8 = 0.2 nm

  Since Arcturus' line has LONGER wavelength, it must be moving AWAY 
  from us.

  Its speed is
                   0.2 nm
          v   =   --------  * c   =   0.000226 * ( 300,000 km/s )  =  68 km/s
                  883.8 nm