Four particles, each carrying a charge of \(|3.0| \mathrm{nC}\), are located at the corners of a square that has a side length of \(50 \mathrm{~mm}\). The charge on the particle at the lower left corner is positive, and the other three particles are negatively charged.

(a) Draw a free-body diagram showing the electric forces exerted on the particle at the upper right corner.

(b) Determine the magnitude and direction of the vector sum of the electric forces exerted on this particle.