A metallic conductor of length 2m and cross-sectional area \( 0.2 \, \text{mm}^2 \) carries a steady current of 1.2 A when a potential difference of 2 V is applied across it. (\( e = 1.6 \times 10^{-19} \), charge density = \( 7.5 \times 10^{28} \, \text{m}^{-3} \))
Then the mobility of the charge carrier is \( x \times 10^{-4} \) SI units. Find \( x \).