Three point charges are arranged at the corners of a square of side as shown. a) what is the potential at the fourth corner (point a)? b) find the magnitude and direction of the electric field at point a. (show your choice of coordinate system.) c) what is the total potential energy of this system? hint: to calculate the total potential energy: re-construct the system by bringing each charge (from infinity) to its current position.

The second largest public utility in the nation is the sole provider of electricity in 32 counties of southern florida. to meet the monthly demand for electricity in these counties, which is given by the inverse demand function p = 1,200 – 4q, the utility company has set up two electric generating facilities: q1 kilowatts are produced at facility 1, and q2 kilowatts are produced at facility 2 (so q = q1 + q2). the costs of producing electricity at each facility are given by c1(q1) = 8,000 + 6q12 and c2(q2) = 6,000 + 3q22, respectively. determine the profit-maximizing amounts of electricity to produce at the two facilities, the optimal price, and the utility company’s profit