Two current-carrying wires are exactly parallel to one another and both carry 3.5 A of current. The two wires are sperated by a distance of 15 cm. The current on wire 1 and wire 2 move down (same direction). What is the magnitude of the magnetic force per unit length cause by wire 1 on wire 2? What is the direction of the magnetic force caused by wire 2 on wire 1?