Kinematics of motion in a straight line — practice question

Particle $A$ is launched vertically upward from point $O$ at a speed of $80\,\text{m s}^{-1}$. After 1 second, a second particle, $B$, which has the same mass as $A$, is launched vertically upward from $O$ at a speed of $100\,\text{m s}^{-1}$. At a time $T\,\text{s}$ after the first particle is launched, the two particles meet and merge to form particle $C$.