function velocityOfSound_psX input SI.Pressure p "Pressure"; input Modelica.SIunits.SpecificEntropy s "Specific entropy"; input Modelica.SIunits.MassFraction X[nC] = reference_X "Mass fraction"; input Properties state; input MultiPhaseMixture.Templates.ExternalObjects.ExternalMediaObject eo "External object"; output Real a; end velocityOfSound_psX;