Two long conductors, separated by a distance $d$ carry current $\mathrm { I } _ { 1 }$ and $\mathrm { I } _ { 2 }$ in the same direction. They exert a force $F$ on each other. Now the current in one of them is increased to two times and its direction reversed. The distance is also increased to $3d$. The new value of the force between them is\\
(1) $-2F$\\
(2) $F / 3$\\
(3) $-2F / 3$\\
(4) $-F / 3$