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   Compute the speed of sound.

   Type SpeedSnd for a demo using Helium.

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   Form:
   a = SpeedSnd( gamma, molWt, T )
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   Inputs
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   gamma         (1,1) Ratio of specific heats
   molWt         (1,1) Average molecular weight of the gas (kg/mole)
   T             (1,:) Temperature (deg-K)

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   Outputs
   -------
   a             (1,:) Speed of sound (m/sec)

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