Help w/ Hubble's Law + Doppler Effect.
Look up the laboratory wavelengths of the Calcium H and K lines
Calculate the redshift implied by the observed wavelengths of the H and K lines.
$$ v/c = (\lambda - \lambda_0)/\lambda_0,$$
where $v$ is the implied recession velocity, $c$ is the speed of light, $\lambda$ is the observed wavelength and $\lambda_0$ is the laboratory wavelength.
Plot recession velocity versus distance and see what you get.
Read about the Hubble redshift-distance relation.