An experimenter arranges to trigger two flashbulbs simultane$-$ously, a blue flash located at the origin of his reference frameand a red flash at x$30\mathrm{.}4$ km$.$ A second observer, moving ata speed $0\mathrm{.}247$cin the direction of increasing x$,$ also views theflashes. $($a$)$ What time interval between them does she find?$($b$)$ Which flash does she say occurs first?