A patient with a pacemaker is mistakenly being scanned for an MRI image. $A 10.0-\mathrm{cm}$ -long section of pacemaker wire moves at a speed of 10.0 $\mathrm{cm} / \mathrm{s}$ perpendicular to the MRI unit's magnetic field and a $20.0-\mathrm{mV}$ Hall voltage is induced. What is the magnetic field strength?