Three Long, Straight, Parallel Wires All Lie in the Yz

Multiple Choice

Three long, straight, parallel wires all lie in the yz plane and each carries a current of 20 A in the positive z direction. The two outer wires are each 4.0 cm from the center wire. What is the magnitude of the magnetic force on a 50-cm length of either of the outer wires?

A) 1.0 mN
B) 0.50 mN
C) 1.1 mN
D) 1.5 mN
E) 2.0 mN