Figure $29-82$ shows, in cross section, two long parallel wires spaced by distance $d=10.0 \mathrm{cm}$ ; each carries 100 $\mathrm{A}$ , out of the
page in wire $1 .$ Point $P$ is on a perpendicular bisector of the line connecting the wires. In unit-vector notation, what is the net magnetic
field at $P$ if the current in wire 2 is (a) out of the page and (b) into the
page?