Hubble Law v = H0 d where v = recessional velocity           d = distance to galaxy          H0 = Hubble constant               = slope of line         H0 = 72 km/s/Mpc (± 10%) i.e. if distance to galaxy increases by 106 pc, galaxy’s recessional speed increases by 72 km/s
		Since time = R / V = d/v = 1 / H0,   t = 106 pc/72 km/s = 106 x 3.08 x 1013/ 72      = 4.3 x 1017 sec      = 14 x 109 yr Hubble constant  Expansion age of universe !!