a
Current carried by conductor, $l=35 \mathrm{A}$
Distance, $r=20 \mathrm{cm}=0.2 \mathrm{m}$
Using Ampere's circuital law we get,
$B=\frac{\mu_{0} l}{2 \pi r}$
$=\frac{4 \pi \times 10^{-7} \times 35}{2 \pi \times 0.20} \mathrm{T}$
$=3.5 \times 10^{-5} \mathrm{T}$