$2.$ The image below shows a parallel plate capacitor that has

cross$-$sectional area A $=10\mathrm{.}5$ cm$^2,$ distance between the two $2$d plates $=7\mathrm{.}12$ mm$.$ Half the left capacitor is filled with a constant dielectric material

electric K$1=21$ and half of the capacitor on the right is filled with two substances

Hilekti$.$ K$2=42$ and K$3=58.$

a$.$ How big is the capacitance of the capacitor?

b$.$ How much energy is stored in the capacitor between the capacitor plates

given a voltage difference of $12$ Volts?

Please show the answer step by step