Answer
$=2.87 \times 10^{-18} \text {. }
$
Work Step by Step
$
\text { The ratio of fields is } \frac{B\left(\text { due to } i_d\right)}{B(\text { due to } i)}\\=\frac{\mu_0 i_d / 2 \pi r}{\mu_0 i / 2 \pi r}=\frac{i_d}{i}\\=\frac{2.87 \times 10^{-16} \mathrm{~A}}{100 \mathrm{~A}}\\=2.87 \times 10^{-18} \text {. }
$
