An Electronic Company has decided tao test three new kinds of light bulbs. They have three identical rooms to use in the experiment. Bulb 1 has an average life time of 1470 hours and a variance of 156. Bulb 2 has an average life time of 1400 hours and a variance of 81. Bulb 3 has an average life time of 1350 hours and a standard deviation of 6 hours. Rank the bulbs in terms of relative variability. Which was the best bulb?