There are two identical barrels in a garden. One is full of rainwater, the other is exactly half full. The barrels weigh 86kg and 53kg, respectively. How much does an empty barrel weigh?
The Empire State Building in New York City has 85 floors of office space, the renting of which creates 37% of the architectural masterpiece's revenue. However, at 40%, the two observation decks are even more lucrative, generating roughly $110 million annually.