If a charged pion that decays in 10* second in its own rest frame is to travel 30 metres in the laboratory before decaying, the pion's speed must be most nearly

If a charged pion that decays in 10* second in its own rest frame is to travel 30 metres in the laboratory before decaying, the pion's speed must be most nearly (1) 0-43x 108 m/s (2) 2-84 x10 m/s (3) 2.90x 108 m/s (4) 2.98x 10 8 m/s