Eight wires cut the page perpendicularly at the points shown in Fig. $30-40 .$ A wire labeled with the integer $k(k=1,2, \ldots,$,
8) carries the current $k i$. For those 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 in the direction shown.