PHYSICS CAPACITORSA parallel$-$plate capacitor has square plates that are $7\mathrm{.}80cm$ on each side and $3\mathrm{.}20mm$ apart. The space between the plates is completely filled with two square slabs of dielectric, each

$7\mathrm{.}80cm$ on a side and $1\mathrm{.}60mm$ thick. One slab is Pyrex glass and the other slab is polystyrene. If the potential difference between the plates is $96\mathrm{.}0V,$ find how much electrical energy $($in $nJ)$

can be stored in this capacitor.