A horizontal overheadpowerline is at height of `4 m` from the ground and carries a current of `100 A` from east to west. The magnetic field directly below it on the ground is
`( nu_(0) = 4 pi xx 10^(-7) Tm A^(-1)`
A. `2.5 xx 10^(-7)` T southward
B. `5 xx 10^(-6) T` northward
C. `5 xx 10^(-6) T` southward
D. `2.5 xx 10^(-7)` northward
