Infinitely long wires parallel to the $y$ - axis are present in the $x-y$ plane at $x = 1, x = 2, x = 4$, and so on. The currents in all the wires with odd serial no is $1A$ in the $+y$ direction while it is $1A$ in the $–y$ direction for all the wires with even serial no. The magnetic field at the origin would be

Question

$\begin {array} {1 1} (a)\;2.67 \times 10^{-7} \hat k & \quad (b)\;1.33 \times 10^{-7} \hat k \\ (c)\;-2.67 \times 10^{-7} \hat k & \quad (d)\;-1.33 \times 10^{-7} \hat k \end {array}$