USAAAO — 2015 First Round

Given that dark energy is vacuum energy, and that the densities of dark energy, dark matter and normal matter in the universe are currently ρ_Λ = 6.7 × 10⁻³⁰ g/cm³, ρ_DM = 2.4 × 10⁻³⁰ g/cm³ and ρ_Λ = 0.5 × 10⁻³⁰ g/cm³, what is the ratio of the density of dark energy at the time of the cosmic microwave background emission, to the current density of dark energy?