\(\mathrm{W}=(-\vec{\mu} \cdot \overrightarrow{\mathrm{B}})_{\mathrm{f}}-(-\vec{\mu} \cdot \overrightarrow{\mathrm{B}})_i\)
\(=0+(\vec{\mu} \cdot \overrightarrow{\mathrm{B}})_i\)
\(=\left(100 \times 5 \times 10^{-3} \times 1 \times 10^{-3}\right) \times 0.2 \mathrm{~J}\)
\(=1 \times 10^{-4} \mathrm{~J}=100 \mu \mathrm{J}\)