Two Tiny Particles Having Charges of +7

Two tiny particles having charges of +7.00 μC and -9.00 μC are placed along the y-axis.The +7.00-µC particle is at y = 0.00 cm,and the other particle is at y = 40.00 cm.Where must a third charged particle be placed along the y-axis so that the net electric force exerted on it by the other two particles is zero?

A) 0.200 m
B) 2.99 m
C) -0.187 m
D) -2.99 m
E) 0.187 m