Step 1: Analysis
When $-2\mu C$ is added to $q_{2}$ ($2\mu C$), the new charge $q_{2}'$ becomes $2 - 2 = 0$.
Step 2: Calculation
According to Coulomb's Law, force is proportional to the product of charges ($F \propto q_{1}q_{2}$).
Step 3: Conclusion
Since one of the charges is now zero, the force becomes zero.
Final Answer: (b)