At what distance from a wire carrying a 10 A current is the magnetic field strength equal to $50\mu \mathrm{T}$ ? This is the approximate value of the earth's magnetic field.

• A. $1.0\mathrm{ cm}$
• B. $2.0\mathrm{ cm}$
• C. $3.0\mathrm{ cm}$
• D. $5.0\mathrm{ cm}$
• E. $6.0\mathrm{ cm}$
• F. $4.0\mathrm{ cm}$