Train cars are coupled together by being bumped into one another. Suppose two loaded train cars are moving toward one another, the first having a mass of 120,000 kg and a velocity of 0.300 m/s, and the second having a mass of 135,000 kg and a velocity of 0.120 m/s. (The minus indicates direction of motion.)

What is their final velocity (in m/s)? (Enter a number.)