Walker, Halliday & Resnick — Magnetic Fields Due to Currents: Problem 24

24 Eight wires cut the page perpendicularly at the points shown in Fig. 29-39. A wire labeled with the integer $k$ ($k = 1, 2, \dots, 8$) carries the current $ki$, where $i = 6.00\text{ mA}$. For those wires with odd $k$, the current is out of the page; for those with even $k$, it is into the page. Evaluate $\oint \vec{B} \cdot d\vec{s}$ along the closed path indicated and in the direction shown.