  We have calculated quark and anti-quark relaxation time by considering
different possible elastic and inelastic scatterings in the medium. Comparative
role of these elastic and inelastic scatterings on different transport
coefficients are explored. The quark-meson effective interaction Lagrangian
density in the framework of Nambu--Jona-Lasinio model is used for calculating
both type of scatterings. Owing to a kinetic threshold, inelastic scatterings
can only exist beyond the Mott line in temperature and chemical potential
plane, whereas elastic scatterings occur in the entire plane. Interestingly,
the strength of inelastic scatterings near and above Mott line becomes so
strong that medium behaves like a perfect fluid, in that all transport
coefficients become very small.
