For a given chemical reaction
$\gamma_1 A+\gamma_2 B \rightarrow \gamma_3 C+\gamma_4 D$
Concentration of C changes from 10 mmol $\mathrm{dm}^{-3}$ to 20 mmol $\mathrm{dm}^{-3}$ in 10 seconds. Rate of appearance of D is 1.5 times the rate of disappearance of B which is twice the rate of disappearance A. The rate of appearance of D has been experimentally determined to be 9 mmol $\mathrm{dm}^{-3} \mathrm{~s}^{-1}$. Therefore the rate of reaction is ________mmol $\mathrm{dm}^{-3} \mathrm{~s}^{-1}$.(Nearest Integer)