A copper wire has a square cross section $2\mathrm{.}4$ mmmm on a side. The wire is $3\mathrm{.}6$ mm long and carries a current of $3\mathrm{.}4$ AA$.$ The density of free electrons is $8\mathrm{.}51028$m$38\mathrm{.}51028$m$3.$ Find the magnitude of the current density in the wire. Find the magnitude of the electric field in the wire. How much time is required for an electron to travel the length of the wire?