A parallel$-$plate capacitor, with air between the plates, is connected across a voltage source. This source establishes a potential difference between the plates by placing charge of magnitude $4\mathrm{.}15{10}^{-6}C$ on each plate. The space between the plates is then filled with a dielectric material, with a dielectric constant of $7\mathrm{.}74.$ What must the magnitude of the charge on each capacitor plate now be$,$ to produce the same potential difference between the plates as before?

$63\mathrm{.}21{10}^{-5}C$

$30\mathrm{.}21{10}^{-5}C$

$23\mathrm{.}21{10}^{-5}C$

$($D$)3\mathrm{.}21{10}^{-5}C$