Coulomb's Law (Finding the force due to two other charge, not only one)

[daimlerpogi]

Homework Statement

In the figure below, determine (a) the electric force on 10 micro Coulomb due to other charges, and (b) the electric force on 2 micro Coulomb due to other charge

Homework Equations

Coulomb's Law

Fe = kq1q2/D²
k = 9.0 x 10^9

The Attempt at a Solution

I really don't know what to do since there are three charges and I should get the Fe due to other two charges. Should I get the Fe in each charge then subtract it?

(a)
10 and 2

Fe = 9x10^9(10x10^-6)(2x10^-6) / 0.005
Fe = 36N

Fe = 9x10^9(10x10^-6)(5x10^-6) / 0.005
Fe = 90N

Fe of 10micro Coulomb = 90 - 36 = 54N?

I really don't know, but I'm trying my best.

 

[buffordboy23]

Pick an origin first. It doesn't really matter where you place it, but I usually place it on the particle that you are trying to determine the E field for. This is a two dimensional problem, so determine the x- and y- components of the force on the particle due to each individual particle. To find the total force on the particle, add the x- and y-components together (principle of superposition); this gives you the force vector acting on the particle.