Explain how does capacitance of a 'parallel plate capacitor change on introducing a 'dielectric slab'?

Explain how does capacity of parallel plate capacitor change on introducing a conducting slab?

The capacitance of a parallel plate capacitor increases with

Derive a relation for the capacitance of a parallel plate capacitor having plate separation d, when a dielectric slab of thickness t is placed between the plates.

Derive an expression for capacitance of a parallel plate capacitor.

On what factors does the capacitance of a parallel plate capacitor with dielectric depend?