For a given chemical reaction ${\mathrm{\gamma }}_1\mathrm{A}+{\mathrm{\gamma }}_2\mathrm{B}\to {\mathrm{\gamma }}_3\mathrm{C}+{\mathrm{\gamma }}_4\mathrm{D}$. Concentration of $\mathrm{C}$ changes from $10 \mathrm{mmol} {\mathrm{dm}}^{-3}$ to $20 \mathrm{mmol} {\mathrm{dm}}^{-3}$ in $10 \mathrm{s}.$ Rate of appearance of $\mathrm{D}$ is $1.5$ times the rate of disappearance of $\mathrm{B}$ which is twice the rate of disappearance $\mathrm{A}$. The rate of appearance of $\mathrm{D}$ has been experimentally determined to be $9 \mathrm{mmol} {\mathrm{dm}}^{-3}{\mathrm{s}}^{-1}.$ Therefore the rate of reaction is____$\mathrm{mmol} {\mathrm{dm}}^{-3}{\mathrm{s}}^{-1}.$ (Nearest Integer)