4. Four identical charges, each having a charge of +q+4x10°C, are fixed at the corners of a square of side L= √8 m. A) Find the electric field at a point P that lies at a distance Z = 2m along the line perpendicular to the plane of the square and passing through the center of the square.(Fig. below) (3pts.) B) Find the net electric force on a fifth point charge +q = 4x10°C, at a point P that lies at Z= 2m above the center of the square due to the other four charges. (2pts.) C) Calculate the potential energy due to the four charge's distribution located on the square (2pt) (use: K = 9 x109 Nm²/C2)