Figure $($a$)$ shows charged particles $1$ and $2$ that are fixed in place on an $x$ axis. Particle $1$ has a charge with a magnitude of $|q_1|=9e.$ Particle $3$ of charge $q_3=+9e$ is initially on the $x$ axis near particle $2.$ Then particle $3$ is gradually moved in the positive direction of th axis. As a result, the magnitude of the net electrostatic force on particle $2$ due to particles $1$ and $3$ changes. Figure $($b$)$ gives the $x$ component of that net force as a function of the position $x$ of particle $3.$ The scale of the $x$ axis is set by $x_5=1\mathrm{.}60m.$ The plot has an asymptote of $F_{2,\text{n}\text{e}\text{t}}=0\mathrm{.}5841{10}^{-25}N$ as $x.$ As a multiple of $e$ and including the sign, what is the charge $q_2$ of particle $2?$

$(a)$

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