The frequency of an electromagnetic wave is $25 \ MHz$. If the magnitude of the electric field at a point at any instant is $6.3 \ V/m$,then the magnitude of the magnetic field at that point is ..... $Wb/m^2$.

• A
  $3.9 \times 10^{-2}$
• B
  $2.5 \times 10^{-7}$
• C
  $2.1 \times 10^{-8}$
• D
  $7.5 \times 10^{-3}$