(solution) Four charged particles are at the corners of a square of side a ,

(solution) Four charged particles are at the corners of a square of side a ,

Four charged particles are at the corners of a square of side a, as shown in the figure below. (A = 4, B = 5, C = 3.)

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(a) Determine the magnitude and direction of the electric field at the location of charge q. (Use k_e for the Coulomb constant and q and a as necessary.) 
Magnitude

(b) What is the total electric force exerted on q
Magnitude