Consider the following single step reaction in gas phase at constant temperature. $$2 \mathrm{~A}_{(\mathrm{g})}+\mathrm{B}_{(\mathrm{g})} \rightarrow \mathrm{C}_{(\mathrm{g})}$$ The initial rate of the reaction is recorded as $\mathrm{r}_1$ when the reaction starts with $1.5 \mathrm{~atm}$ pressure of $\mathrm{A}$ and $0.7 \mathrm{~atm}$ pressure of B. After some time, the rate $r_2$ is recorded when the pressure of C becomes $0.5 \mathrm{~atm}$. The ratio $\mathrm{r}_1: \mathrm{r}_2$ is $\underline{\hspace{2cm}}$$\times 10^{-1}$. (Nearest integer)