Answer :
Use Doppler's formula to find the radial velocity of star.
[tex]\frac{V_r}{c} = \frac{\Delta \lambda}{\lambda_0}[/tex]
Here,
[tex]V_r[/tex] = Radial Velocity
c = Speed of light
[tex]\Delta \lambda[/tex] = Shift in wavelength
[tex]\lambda_0[/tex] = Laboratory wavelength of spectral line
Rearrange for [tex]V_r[/tex],
[tex]V_r = \frac{\Delta \lambda}{\lambda_0} c[/tex]
Find shift in wavelength, [tex]\Delta \lambda[/tex]
[tex]\Delta \lambda = |485.5nm - 486.1nm|[/tex]
[tex]\Delta \lambda = 0.6nm[/tex]
Replacing our values we have then,
[tex]V_r = \frac{0.6nm}{486.1nm}(3*10^8m/s)[/tex]
[tex]V_r = 370000m/s[/tex]
Therefore the radial velocity of star is [tex]3.7*10^5[/tex]m/s
In this case the symbol of [tex]\Delta \lambda[/tex] implies that the star is receding the observer and the wavelength turns to red, then is red shifted.