  We extract the effective degrees of freedom that characterize the co-existing
phase of quark gluon plasma and hadrons. Experimental data on phi at
mid-rapidity is used to set a lower bound to the critical temperature of quark
hadron phase transition. The production and evolution of strangeness have been
studied by using Boltzmann equation. The results have been contrasted with the
experimental data obtained by STAR collaboration at RHIC for Au + Au collisions
at sqrt{s_{NN}}=200 GeV. Our study reveals that the phi mesons freeze out at a
temperature ~ 160 MeV, a value close to the transition temperature for
quark-hadron phase transition.
