A polymer chain in a melt has degree of polymerization between entanglements

$N_e=500.$ Estimate characteristic relaxation time of chains with the degrees of

polymerizations equal to $200$ and $2000,$ if the relaxation time of a repeat unit ${}_0=1\mathrm{.}0$

nsec$.$ Use for the repeat unit projection length $0\mathrm{.}25nm$ and for the Kuhn length $2\mathrm{.}0nm.$