You observe a binary star system where a small star orbits around a stationary large star. A spectral line in the spectrum of the small star is redshifted by $0\mathrm{.}162$ nm when the star is at a point on its orbit when it is moving away from the Earth. The wavelength of this spectral line would be observed at $625\mathrm{.}000$ nm if the star were at rest relative to you. You can assume that this shift in wavelength is only due to the orbital motion of the star.