Three charges are located at three corners of a square as shown in the figure. [Answer in 3 significant figures)

A. How much work is required to bring in a fourth charge (94=+4.0 C) to the last corner of the square at constant speed?

B. What is the net electric field magnitude and direction at the center of the square due to the four charges?

C. Sketch the electric field for the system (you need to have at least 5 field lines for the smallest charge)