What Is the Correct Value of q in Coulomb's Law Problem?

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The net force on a 1nC charge is zero, and the discussion revolves around determining the value of charge q, which is positioned 2cm above the 1nC charge. Three forces are acting on the 1nC charge: two from charges located below and to the sides of q, and one from q itself. The calculated forces from the two bottom charges are approximately 9.79e-6 in both the i and j directions, while the force from q is significantly larger at -22500q in the j direction. The final equation used to solve for q resulted in a value of 0.870nC, which contradicts the book's answer of 0.68nC. The discussion suggests a potential oversight in the calculations leading to the discrepancy.
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The net force on a 1nC charge is 0. What is q?

There are 3 forces. q is 2cm in the y direction away from a charge of 1nC. Another charge of 2nC is 4cm below q and 3cm to the right. The final charge is 4cm below q and 3cm to the left. Using Coulomb's law, I found the force of the two bottom charges to be 9.79e-6i+9.79e-6j and -9.79e-6i+9.79e-6j respectively. The final charge I found to be -22500q in the j direction. By adding all the forces together I find q to be 0.870nC. The answer in the back of the book is 0.68nC. Where have I gone wrong?

My final equation to solve for q was 1.96e-5 = 22500q
 
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Force from first charge + Force fromsecond charge + Force from q = Force on 1nC charge = 0.

I think you missed this part which is why your off.
 

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