A singly ionized (one electron removed) 40K atom passes through a velocity selector consisting of uniform perpendicular electric and magnetic fields. The selector is adjusted to allow ions having a speed of 4.50 km/s to pass through undeflected when the magnetic field is 2.50×10⁻² T. The ions next enter a second uniform magnetic field (B') oriented at right angles to their velocity. 40K contains 19.0 protons and 21.0 neutrons and has a mass of 6.64×10⁻²⁶ kg.

What is the magnitude of the electric field in the velocity selector?