The horizontally placed conductors of a single phase line operating at $50$ $Hz$ are having outside diameter of $1.6$ $cm$, and the spacing between centers of the conductors is $6$ $m$. The permittivity of free space is $8.854\times 10^{-12}F/m$. The capacitance to ground per kilometer of each line is
1. $4.2\times 10^{-9}F$
2. $8.4\times 10^{-9}F$
3. $4.2\times 10^{-12}F$
4. $8.4\times 10^{-12}F$