An isolated parallel-plate capacitor of areaA1with an air gap of lengths1is charged up to a potential differenceV1. A second parallel-plate capacitor, initially uncharged, has an area A2and a gap of lengths2filled with plastic whose dielectric constant isK. You connect a wire from the positive plate of the first capacitor to one of the plates of the second capacitor, and you connect another wire from the negative plate of the first capacitor to the other plate of the second capacitor. What is the final potential difference across the first capacitor? (Use any variable or symbol stated above as necessary.)

Vf=