Answer
$B_{max}=1.33\times 10^{-10}T$
Work Step by Step
To find the maximum magnitude of the magnetic field, use the relation that $$E_{max}=cB_{max}$$ Solving for $B_{max}$ yields $$B_{max}=\frac{E_{max}}{c}$$ Substituting known values of $E_{max}=0.0400V/m$ and $c=3.00\times 10^8m/s$ yields a maximum magnitude of $$B_{max}=\frac{0.0400V/m}{3.00\times 10^8m/s}=1.33\times 10^{-10}T$$
