A single circular loop of wire has a radius of $2.0\mathrm{cm}$, and carries a current of $4.0\text{A}$. What is the maximum torque that could be experienced by this loop due to earth's magnetic field?

• A. $2.5\times {10}^{-8}\mathrm{N}\cdot \mathrm{m}$
• B. $6.3\times {10}^{-8}\mathrm{N}\cdot \mathrm{m}$
• C. $8.0\times {10}^{-8}\mathrm{N}\cdot \mathrm{m}$
• D. $1.8\times {10}^{-7}\mathrm{N}\cdot \mathrm{m}$
• E. $7.9\times {10}^{-7}\mathrm{N}\cdot \mathrm{m}$
• F. $2.5\times {10}^{-7}\mathrm{N}\cdot \mathrm{m}$