A railway truck \( A \) of mass \( 2000 \mathrm{~kg} \) moves westwards with a velocity of \( 3 \mathrm{~m} \cdot \mathrm{s}^{-1} \). It collides with a stationary truck B of mass \( 1200 \mathrm{~kg} \), loaded with electronic equipment of mass \( 300 \mathrm{~kg} \). The two trucks combine after the collision. Ignore the effects of friction. What is the velocity of truck B after the collision