Flow of Electrons in a Metal, Drift Velocity, Relaxation Time, Mobility and Simple Derivation of Ohm's Law

Estimate the average drift velocity of the conduction electrons in a copper wire of cross section $2.0\times {10}^{-3}{\mathrm{cm}}^2$ carrying a current of 

$2.0 \mathrm{A}$ Assuming the density of conduction electrons to be $9\times {10}^{28}{\mathrm{m}}^{-3}$.