A current of 16 A is made to pass through a conductor in which the number density of free electrons is $4 \times 10^{28}m^{-3}$ and its area of cross section is $10^{-5}m^2$. The average drift velocity of free electrons in the conductor is

Question

$\begin {array} {1 1} (1)\;2.5 \times \: 10^{-4}m.s^{-1} & \quad (2)\;3.2 \times \: 10^{-4}m.s^{-1} \\ (3)\;6.4 \times \: 10^{-4}m.s^{-1} & \quad (4)\;1.6 \times \: 10^{-4}m.s^{-1} \end {array}$