The vector position of a $$3.50-g$$ particle moving in the $$xy$$ plane varies in time according to $$\vec{r}_{1}=(3\hat{i}+3\hat{j})t+2\hat{j}t^{2}$$, where $$t$$ is in seconds and $$\vec{r}$$ is in centimeters. At the same time, the vector position of a $$5.50\ g$$ particle varies as $$\vec{r}_{2}=3\hat{i}-2\hat{i}t^{2}-6\hat{j}t$$. At the $$t=2.50\ s$$, determine
the vector position of the center of mass.