A $5\mathrm{.}0C$ charge is positioned at the origin, and a second charge is placed on the x $-$axis at $x-0\mathrm{.}2m.$ If the force on the second charge is $3\mathrm{.}5$ N in the positive $x-$direction, what is the magnitude of its charge?

$-3\mathrm{.}9C$

$3\mathrm{.}1C$

$0C$

$3\mathrm{.}9C$

$-3\mathrm{.}1C$