in a particular inertial frame s, two events occur a distance c△t apart and one event occurs before the other by a time at. an observer who is travelling at speed v relative to s in a direction parallel to the line joining the events notes that the events are only δt/2 apart. determine v/c. 8 marks c) a second observer is travelling in the same direction as the first observer but at a speed of 4c/5 as measured in s. in terms of δt, what is the time interval between the events according to this observer? [5 marks) d) what is the speed of the second observer as determined in the rest-frame of the first 6 marks observer?