Some animals are capable of detecting magnetic fields and use this sense to help them navigate. Suppose a high-voltage directcurrent power line carries a current of 5.0 kA. 

(a) How far from the wire would a homing pigeon have to be so the field due to the wire has magnitude 45 μT, which is comparable to Earth's magnetic field at the surface? 

(b) On a long-distance flight, the pigeon is flying at an altitude of 700 m. What would the magnetic field be at that distance from the power line? If the homing pigeon navigates by sensing the magnetic field, might the power line disrupt its ability to navigate on a long-distance flight?