Momentum — practice question

Particles $P$ and $Q$, whose masses are $0.2\,\text{kg}$ and $0.3\,\text{kg}$ respectively, are able to move only along a horizontal straight line on a smooth horizontal plane. $P$ is launched towards $Q$ at speed $0.5\,\text{m s}^{-1}$. Simultaneously, $Q$ is launched towards $P$ at speed $1\,\text{m s}^{-1}$. In the collision that results, $Q$ is brought to rest.