a) During a lightning flash, -12 C of charge moves through a potential difference of 8.2x10⁷ V . Determine the change in electric potential energy of the field-charge system. Express your answer to two significant figures and include the appropriate units.

b) Four objects with the same charge -q are placed at the corners of a square of side d . Determine the value of the E^→ field in the center of the square. Express your answer in terms of some or all of the variables k, q, and d. Determine the value of the V field in the center of the square. Express your answer in terms of some or all of the variables k, q, and d.