Suppose that A' , B', and C' are at rest in frame S', which moves with respect to S at speed v in the +x direction. Let B' be located exactly midway between A' and C'. At t' = 0, a light flash occurs at B' and expands outward as a spherical wave.

(a) According to an observer in S', do the wave fronts arrive at A' and C' simultaneously? 

(b) According to an observer in S, do the wave fronts arrive at A' and C' simultaneously? 

(c) If you answered no to either (a) or (b), what is the difference in their arrival times and at which point did the front arrive first?