In the figure the four particles form a square of edge length $a=5\mathrm{.}00cm$ and have charges $q_1=8\mathrm{.}19nC,q_2=-19\mathrm{.}5nC,q_3=19\mathrm{.}5nC,$ and $q_4=-8\mathrm{.}19nC.$ What is the magnitude of the net electric field produced by the particles at the square's center?

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