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?