$12\mathrm{.}104$ A mixture of $60\%$ ethylene and $40\%$ acetylene by moles is at $6$MPa,$300K.$ The mixture flows through a preheater, where it is heated to $400K$ at constant $P.$ Using the Redlich$-$Kwong EOS with $a,b$ for a mixture, find the inlet specific volume. Repeat using Kay's rule and the generalized charts.