Answer
$2.4\times10^{-13}T$
Work Step by Step
Use equation 22–2.
$$c=\frac{E}{B}$$
Here, E and B are the magnitudes of the electric and magnetic fields at the same point in space. Both fields reach their maximum at the same place.
$$B=\frac{E}{c}=\frac{0.72\times10^{-4}V/m}{3.00\times10^8m/s}=2.4\times10^{-13}T$$