1. The problem statement, all variables and given/known data High resolution spectroscopy reveals that the H line is located at a wavelength of 656.250 nm for this star. The wavelength of H measured in the lab is 656.280 nm. Calculate the line-of-sight velocity of the star. 2. Relevant equations Here's the Doppler formula: Vr = (Δλ/λ0)c where Vr is the radial speed of the star, Δλ is the Doppler shift, λ0 is the rest wavelength or the wavelength measured in the lab, and c is the speed of light. 3. The attempt at a solution I'm just having trouble with units. I need the answer (the radial speed of the star) in km/s, but i don't know what units to put the other variables (Δλ, λ0, c) in.