Two Tiny Particles Having Charges Of $+ 7.00 \mu \mathrm { C }$

Two tiny particles having charges of $+ 7.00 \mu \mathrm { C }$ and $- 9.00 \mu \mathrm { C }$ are placed along the $y$ -axis. The $+ 7.00 - \mu \mathrm { C }$ particle is at $y = 0.00 \mathrm {~cm}$ , and the other particle is at $y = 40.00 \mathrm {~cm}$ . Where must a third charged particle be placed along the $y$ -axis so that it does not experience any net electric force due to the other two particles?

A) $2.99 \mathrm {~m}$
B) $- 2.99 \mathrm {~m}$
C) $0.187 \mathrm {~m}$
D) $0.200 \mathrm {~m}$
E) $- 0.187 \mathrm {~m}$