In order to calculate the force between the charges, we can use the formula below:
[tex]F=\frac{KQq}{d^2}[/tex]
Where K is the electrostatic constant (K = 9 * 10^9), Q and q are the charges and d is the distance between them (in meters).
So we have:
[tex]\begin{gathered} F=\frac{9\cdot10^9\cdot500\cdot10^{-6}\cdot100\cdot10^{-6}}{0.5^2}\\ \\ F=\frac{450}{0.25}\\ \\ F=1800\text{ N} \end{gathered}[/tex]
Therefore the correct option is the second one.
