181. Three fixed point charges are arranged as shown in the figure below. The electric field at point O due to the three charges is $100\,\dfrac{\text{N}}{\text{C}}$. $$\left(k = 9\times10^9\,\frac{\text{N}\cdot\text{m}^2}{\text{C}^2}\right)$$ How many nanocoulombs can $q_2$ be? [Figure: Three charges on a line: $q_1 = 8\,\text{nC}$ at left, $q_2 = ?$ in middle, $q_3 = -2\,\text{nC}$ at right, point O at far right; distances of 10 cm between each]
[(1)] $+4$
[(2)] $+2$
[(3)] $-2$
[(4)] $-4$
\textbf{181.} Three fixed point charges are arranged as shown in the figure below. The electric field at point O due to the three charges is $100\,\dfrac{\text{N}}{\text{C}}$.
$$\left(k = 9\times10^9\,\frac{\text{N}\cdot\text{m}^2}{\text{C}^2}\right)$$
How many nanocoulombs can $q_2$ be?
\textit{[Figure: Three charges on a line: $q_1 = 8\,\text{nC}$ at left, $q_2 = ?$ in middle, $q_3 = -2\,\text{nC}$ at right, point O at far right; distances of 10 cm between each]}
\begin{itemize}
\item[(1)] $+4$
\item[(2)] $+2$
\item[(3)] $-2$
\item[(4)] $-4$
\end{itemize}