EAMCET Engineering 2003 Solved Paper

An infinite number of electric charges each equal to 5 nano-coulomb (magnitude) are placed along X-axis at x=1‌cm,x=2‌cm, x=4‌cm,x=8‌cm.... and so on. In this set up if the consecutive charges have opposite sign, then the electric field in newton/coulomb at x=0 is :
(‌

1

4πε0

=9×109N−m2∕C2)