An astrophysicist studying a distant galaxy identifies the Hydrogen-alpha (Hα\text{H}_\alphaHα) spectral line in its emission spectrum. The laboratory wavelength of this line is λ0=656.3 nm\lambda_0 = 656.3\text{ nm}λ0=656.3 nm, but the observed wavelength from the galaxy is λ=688.5 nm\lambda = 688.5\text{ nm}λ=688.5 nm. Using a Hubble constant of H0=70 km s−1 Mpc−1H_0 = 70\text{ km s}^{-1}\text{ Mpc}^{-1}H0=70 km s−1 Mpc−1 and the speed of light c=3.00×108 m s−1c = 3.00 \times 10^8\text{ m s}^{-1}c=3.00×108 m s−1, what is the approximate distance to this galaxy?
200 Mpc200\text{ Mpc}200 Mpc
210 Mpc210\text{ Mpc}210 Mpc
4500 Mpc4500\text{ Mpc}4500 Mpc
2.1×105 Mpc2.1 \times 10^5\text{ Mpc}2.1×105 Mpc