1. Two puppies are fighting over a toy. Each puppy grips one end of that toy in its mouth and pulls. Suddenly, the puppy on the right pulls especially hard on the toy and moves its end of the toy to the right. The other puppy manages to keep its end of the toy from moving. Alas, the toy breaks and the game ends. Breaking the toy required energy and that energy was provided

• only by the puppy on the right.
• by both puppies, but most was provided by the puppy on the right.
• only by the puppy on the left.
• in equal amounts by the two puppies.