Two particles having position vectors r_1 =(2 i +3 j ) m and r_2 =(-10 i +3 j ) m are moving with velocities v_1 =( i -2 j ) m / s and v_2 =(5 i -b j…

Two particles having position vectors $\displaystyle \overrightarrow{r_1}=(2 \vec{i}+3 \vec{j}) \mathrm{m}$ and $\displaystyle \overrightarrow{r_2}=(-10 \vec{i}+3 \vec{j}) \mathrm{m}$ are moving with velocities $\displaystyle \overrightarrow{v_1}=(\vec{i}-2 \vec{j}) \mathrm{m} / \mathrm{s}$ and $\displaystyle \overrightarrow{v_2}=(5 \vec{i}-b \vec{j}) \mathrm{m} / \mathrm{s}$. If they meet after $\displaystyle 3$ second, the value of ' $\displaystyle b$ ' is \_\_\_\_.