Spacecraft I, containing students taking a physics exam, approaches the Earth with a speed of 0.700c (relative to the Earth), while spacecraft II, containing professors proctoring the exam, moves at 0.300c (relative to the Earth) directly toward the students. The professors stop the exam after 80.0 min have passed on their clock.
(a) For what time interval does the exam last as measured by the students?
(b) For what time interval does the exam last as measured by an observer on Earth?