$3\mathrm{.}5$ kg$/$h of water solution of H$2$SO$4,$ at $40\%$wt in acid at $90\backslash$deg C are mixed isothermally with $2$ kg$/$h of water solution of H$2$SO$4$ at $80\%$wt at $90\backslash$deg C$.$ Estimate the heat flow in Kcal$/$h$.$It is mondatory use Enthalpy$-$Concentration diagram to solve this exercise.