A piece of work can be done by 16 men in 8 days working 12 hours a day. How many men are needed to complete another work, which is three times the first one, in 24 days working 8 hours a day?
A commodity market has a _________ structure, if there is one seller of the commodity, the commodity has no substitute, and entry into the industry by another firm is prevented.
A boy leaves his school and travels 8 km towards the east. He takes a left turn and travels 6 km in that direction, and then turns towards the east and travels another 5 km. Finally, he turns right and travels 10 km. In which direction is he now from his school?