Three point charges \( q \), \( -2q \) and \( 2q \) are placed on x-axis at a distance \( x=0 \), \( x=\dfrac{3}{4}R \) and \( x=R \) respectively from origin as shown. If \( q=2\times 10^{-6} \, \text{C} \) and \( R=2 \, \text{cm} \), the magnitude of net force experienced by the charge \( -2q \) is __________ \( \text{N} \).
