One of the first rules we learn in physics is that energy can never be created or destroyed, only transformed.
Much of the modern world is driven by transforming electricity into different forms of power. Speakers turn electrical power into sound. Light bulbs turn electrical power into light. Motors and generators turn electrical power into mechanical power and back, respectively. Keeping track of how electrical power is transferred and transformed is essential to making energy-efficient technologies.
Today's challenge involves a circuit with bulbs in parallel, so if you are unfamiliar with this kind of design, keep reading. If you feel ready, you can jump straight to today's challenge.