(a) If the bottom of a thundercloud has a potential of −1.00 × 10⁹ V with respect to Earth and a charge of −20.0 C is discharged from the cloud to Earth during a lightning strike, how much electric potential energy is released? (Assume that the system acts like a capacitor—as charge flows, the potential difference decreases to zero.) 

(b) If a tree is struck by the lightning bolt and 10% of the energy released vaporizes sap in the tree, how much sap is vaporized? (Assume the sap to be water initially at 20°C.) 

(c) If 10% of the energy released from the lightning strike could be stored and used by a homeowner who uses 400 kW·hr of electricity per month, for how long could the lightning bolt supply electricity to the home?