10. For Omega=0, the expansion rate da/dt is constant, so a₀=t₀da/dt, and therefore
t₀=1/H₀=1.4x10¹⁰yr (for H₀ =70 km/s/Mpc).

If Omega>0 then the age will be less, since expansion will have slowed, and must therefore have been faster in the past (so it needed less time to get to the present scale).