b
$\overrightarrow{\mathrm{M}}=\mathrm{iA}$
$=5 \times(0.2) \times(0.1)(-\hat{\mathrm{i}})$
$=0.1(-\hat{\mathrm{i}})$
$\vec{\tau}=\overrightarrow{\mathrm{M}} \times \overrightarrow{\mathrm{B}}=0.1(-\hat{\mathrm{i}}) \times\left(2 \times 10^{-3}\right)(\hat{\mathrm{j}})$
$=2 \times 10^{-4}(-\hat{\mathrm{k}}) \mathrm{N}-\mathrm{m}$
