Observer a, who is at rest in the laboratory, is studying a particle that is moving through the laboratory at a speed of v-0.8c and determines its lifetime to be ta-107 ns. observer a places markers in the laboratory at the locations where the particle is produced and where it decays. how far apart are those markers in the laboratory? (b) observer b, who is traveling along with the particle, observes the particle to be at rest and measures its lifetime to be tb-136 ns. according to b, how far apart are the two markers in the laboratory?