Two bodies of masses 40 kg and 60 kg collide with each other when coming from opposite sides with velocities of \( 10\ {\rm ms}^{-1} \) and \( 5\ {\rm ms}^{-1} \) respectively and then get stuck and move together. What will be the velocity of the two bodies after collision?

A \( 2.5{\rm ms}^{-1} \)

B \( 2{\rm ms}^{-1} \)

C \( 1.5{\rm ms}^{-1} \)