Walker, Halliday & Resnick — Magnetic Fields Due to Currents: Problem 19

19 Figure 29-35 shows a cross section of a long thin ribbon of width $w = 6.20\text{ cm}$ that is carrying a uniformly distributed total current $i = 4.61\text{ mA}$ into the page. In unit-vector notation, what is the magnetic field at a point $P$ in the plane of the ribbon at a distance $d = 1.61\text{ cm}$ from its edge? (Hint: Imagine the ribbon as being constructed from many long, thin, parallel wires.)