Answer:
B = 0.009 T
Step-by-step explanation:
The magnetic force is given by 
 F = q vx B = i L x B 
Bold quantities refer to vectors. 
 
We are given some data the current (i 14.7 A), the force per unit length (F/L= 0.125 N / m) 
We can take off in magnetic field since the current and the field are perpendicular, so the sine 90 = 1, write the magnitude of the equation 
F = i L B 
B = (F / L) 1 / i 
B = 0.125 1/14.7 
B = 0.009 T