Answer:
1.58 m/s
Step-by-step explanation:
By the conservation of momentum, we can write the following equation

Where m1 is the mass of the first car, v1i is the speed of this car, m2 is the mass of the second car and vf is the final speed. So, we need to solve for vf as

Replacing m1 = 13,500 kg, v1i = 4.5 m/s, and m2 = 25,000 kg, we get

Therefore, the speed of the two cars after the collision is 1.58 m/s