Three charges are located at three corners of a square as shown in the figure. [Answer in 3 significant figures] y +2.0 JC 4 cm X 4 cm -1.0 JC -1.0 JC a) [10 pts] How much work is required to bring in a fourth charge (q4=-4.0 JC) to the last corner of the square at constant speed? b) [14 pt] What is the net electric field magnitude and direction at the center of the square due to the four charges? c) [6 pts] Sketch the electric field for the system (you need to have at least 5 field lines for the smallest charge)