Writhe the problem, given, unkown, formula and final answer.

3. The voltage across an air-filled parallel-plate capacitor is measured to be 90.0 V. When a dielectric is inserted and completely fills the space between the plates, the voltage drops to 35.0 V. What is the dielectric constant of the inserted material? 4. A 12.0-V battery is connected to a 4.5-uF capacitor. How much energy is stored in the capacitor