An electron of = 0.999 987 moves along the axis of an evacuated tube that has

An electron of β = 0.999 987 moves along the axis of an evacuated tube that has a length of 3.00 m as measured by a laboratory observer S at rest relative to the tube. An observer S' at rest relative to the electron, however, would see this tube moving with speed v (= βc). What length would observer S' measure for the tube?