Four identical positive point charge q are placed at the corner of a square plate of side ‘d’. Another point fixed charge q is placed at a distance ‘d/2’ from the centre of square as shown. Choose the correct options.

Usys=4kq2d+2kq22d+8kq23d=2kq2d22+1+423​Potential at the centre​Vf=42kqd+2kqdWork done = q0Vf−Vi=222+1kqq0d​The flux of charge at corners of square is zero.​Imagine a cube of side d , with q at its center.ϕcube=qε0​⇒ϕface=q6ε0