When a volcano erupts, it sends ash into the upper atmosphere, partially blocking out the sun, and thus reducing the amount of electric power generated by solar panels. During the 35- year period 1980–2015, there were four volcanic eruptions sufficiently powerful to reduce the amount of power generated by solar panels by at least 20% for a period of a year. We will call these “Class D20” volcanoes. Solar panels typically have a 25-year warranty, and therefore the return on investment from installing solar panels is often calculated over a 25-year period. What is the probability that, during a 25-year period, there will be two or more “Class D20” volcanic eruptions?