A 15-Mg car 'A' is moving on a horizontal track at a velocity of 1.5 m/s, when it collides with a 12-Mg car 'B' moving towards it at a velocity of 0.75 m/s. If the cars meet and get coupled together, find the speed of both cars immediately after the coupling.
1
0.5 m/s
2
2 m/s
3
1.5 m/s
4
1 m/s