49. A ship sails downstream from Port A to Port B, and upon arrival, immediately returns upstream to Port A, taking a total of 12 hours. It is known that the ship travels 16 kilometers more per hour downstream than upstream, and it also travels 80 kilometers more in the first 6 hours than in the last 6 hours. Therefore, the distance between Port A and Port B is $\qquad$ kilometers.
Answer: 280