Figure below shows a central charge surrounded by several charges arranged on a square. The distance between the adjacent surrounding charges are either d or $2$d$.$ Let$$s assume q $=5$ nC $($ n $=$ nano $=10-9)$ and d $=15$ cm$.$ What is the direction and magnitude of the net electric force on the central particle? $($Hint: First, apply symmetry to cancel out equal and opposite forces!$)$