Event A happens at the space time coordinates (x, y, z, t) = (2 m, 3 m, 0, 0.1 s) and event B happens at the space time coordinates (x, y, z, t) = (0.4 × 108 m, 3 m, 0, 0.2 s).
(a) Is it possible that event A caused event B?
(b) If event B occurred at (0.2 × 108 m, 3 m, 0, 0.2 s) instead, would it then be possible that event A caused event B?