A particle is moving at a speed of 2.6x10° ms relative to the laboratory. it s lifetime as measured by an observer in the laboratory is 4.7x10 s. the lifetime o

A particle is moving at a speed of 2.6x10° ms relative to the laboratory. It s lifetime as measured by an observer in the laboratory is 4.7x10 s. The lifetime of the particle in its Own rest frame is about (a) 2.3x 10 s (b) 9.4x 10 s (c) 4.7x10 s (d) 14.4x10* s