A certain capacitor has a capacitance of 5.0 μF. After it is charged to 5 μC and isolated, the plates are brought closer together so its capacitance becomes 10 μF. The work done by the agent is about: 0 J 1.25×10−6 J −1.25×10−6 J 8.3×10−7 J −8.3×10−7 J