请帮忙解一道中学数学题！谢谢！

"NASA Explorer Schools's students traveled on four buses to Goddard Space Flight Center. Each pair of students was exactly matched with one teacher chaperone, and each teacher chaperone was matched with exactly one pair of students. If each bus could hold 57 passengers and no more than the necessary number of buses was used, what is the positive difference between the maximum and minimum number of students that could have been on the buses?"

By the way this Math problem is fo8th grade students.