current runs from infinity to origin via the x axis, then veers right and goes out to infinity again via the y axis. find magnetic field intensity H at P(0,0,1).
the biot-savart formula introduces a deceptively easy looking integrand that will eat your lunch. unless you have a cheat sheet in your back pocket, or a computer, you will have to be, how do they say, clever about solving it. follow the above link, and choose three down and one to the right.
electromagnetics is interesting in that you can think you are very much more informed than people 150 years ago, yet you find yourself wanting for their pencil and paper skills. if you can't draw a triangle and make a few substitutions, there's no point attempting to solve for the EM plane wave, i should think. but i don't think 90% of EE majors can do this kind of thing anymore, or else i would have been taught by now.