Question

a conductor which is an endless strip has width b.
current "I" goes threw it by its length(from left to right)
the current flows threw y axes the z axes is pointed up.
cyrrent density is j
calculate the magnetic feild on each point in z axes

here again i dont know how they devide the strip
how they integrate it?

if someone coud make sense in it
[IMG]http://i51.tinypic.com/2me2wdl.jpg[/IMG]