The Figure Shows a Cross Section of Three Parallel Wires

Multiple Choice

The figure shows a cross section of three parallel wires each carrying a current of 24 A. The currents in wires B and C are out of the paper, while that in wire A is into the paper. If the distance R = 5.0 mm, what is the magnitude of the force on a 4.0-m length of wire A?

A) 15 mN
B) 77 mN
C) 59 mN
D) 12 mN
E) 32 mN