Have you ever listened for an approaching train by kneeling next to a railroad track and putting your ear to the rail? Young's modulus for steel is Y = 2.0 1011 N/m2, and the density of steel is rho = 7860 kg/m3. On a day when the temperature is 19° C, how many times greater is the speed of sound in the rail than in the air? (Treat air as an ideal gas of particles with mass 4.78 10-26 kg and with γ = 1.40.)