Six identical positive charges, q=10-13 C are placed, one at each vertex of a regular hexagon in the x-y plane centered

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Six identical positive charges, q=10-13 C are placed,
one at each vertex of a regular hexagon in the x-y plane centered
at the origin. Let the charges be numbered with the index j from 1
to 6. The position of the j-th charge is xj=a cos(j
π/3), yj=a sin(j π/3) where a=3 mm and j=1,2,…,6.
Calculate the magnitude of the electric field created by the system
of five charges at the location of the sixth charge
(j=6).