The Proper Mean Lifetime of a Muon Is 2

The proper mean lifetime of a muon is 2.2 × 10^-6 s. A beam of muons is moving with speed 0.6c relative to an inertial observer. Approximately how far will a muon in the beam travel, on average, before it decays?

A) 288 m
B) 360 m
C) 500 m
D) 600 m
E) 800 m