A capacitor has capacitance 5$$\mu$$F when it's parallel plates are separated by air medium of thickness d. A slab of material of dielectric constant 1.5 having area equal to that of plates but thickness $$\frac{d}{2}$$ is inserted between the plates. Capacitance of the capacitor in the presence of slab will be __________ $$\mu$$F.

A parallel plate capacitor with air between the plate has a capacitance of 15pF. The separation between the plate becomes twice and the space between them is filled with a medium of dielectric constant 3.5. Then the capacitance becomes $$\frac{x}{4}$$ pF. The value of $$x$$ is ____________.

As show in the figure, in steady state, the charge stored in the capacitor is ____________ $$\times\, 10^{-6}$$ C.

A parallel plate capacitor with width $$4 \mathrm{~cm}$$, length $$8 \mathrm{~cm}$$ and separation between the plates of $$4 \mathrm{~mm}$$ is connected to a battery of $$20 \mathrm{~V}$$. A dielectric slab of dielectric constant 5 having length $$1 \mathrm{~cm}$$, width $$4 \mathrm{~cm}$$ and thickness $$4 \mathrm{~mm}$$ is inserted between the plates of parallel plate capacitor. The electrostatic energy of this system will be ____________ $$\epsilon_{0}$$ J. (Where $$\epsilon_{0}$$ is the permittivity of free space)