4. Two long straight wires are separated by a distance 2a as shown in Figure 5. The currents are /1 - 15.0 A to the left in the upper wire and /2 - 10.0 A to the right in the lower wire. The distance a - 8.00 cm. 6 2a a 12 8 P2 Figure 5. a) What is the magnitude and direction of the magnetic field at P1? b) What is the magnitude and direction of the magnetic field at P2? c) What is the magnitude of the force per unit length the wires exert on each other? What is the direction of the force acting on upper wire? (use up or down to indicate your direction)