Four charges are placed at the corners of a square, where q is positive (q > 0). initially there is no charge in the center of the square.

a) find the work w required to bring the charge qf = +q from infinity and place it at the center of the square.

b) what is the magnitude of the electric force on the charge q when it is placed at the center of the square?

c) what is the magnitude of the total electrostatic energy of the system?

d) what is the sign of the total energy associated with the five point charges?