b) In a reference frame S, an event 1 occurs at the origin at t = 0 and another event 2 occurs at x = 4000 m and time t = 5x10-6 s. Find the time interval between the events as registered by clock in a frame S' moving with speed v = 0.6c relative to S along the common X-X' axis, the origin coinciding at t = t' = 0. 10