Suppose that A$,$ B$,$ and C$$ are three points along the x$$ axis at rest in frame S$.$ The frame S$$ moves with respect to S at speed v in the $+$x direction. Let B$$ be located exactly midway between A$$ and C$,$ so that A$$B$=$ B$$C $=$ L$.$ At t $=0,$ a light flash occurs at B$$ and expands outward as a spherical wave. $1.($a$)$ According to an observer in S$,$ do the wave fronts arrive at A$$ and C$$ simultaneously? $2.($b$)$ According to an observer in S$,$ do the wave fronts arrive at A$$ and C$$ simultaneously? $13.($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?