I think its between b or c
Answer:
For the first situation, we first need to find the mass of the second train car.
In order to do that, we apply the conservation of the amount of movement:

and we have as a result:
m2 = 289.6875
For the second situation, also we will apply the conservation of the amount of movement:

and we have as a result:
V = 2.64 (it is moving to the right)
D=Vot+1/2at^2
In this case, there is no initial y velocity so the term Vot=0 so d=1/2at^2
acceleration=acceleration due to gravity=-9.8m/s^2
It falls - 22cm or -0.22m
We have - 0.22=1/2(-9.8)t^2
t^2=(-0.44)/(-9.8)
t=sqrt[0.44/9.8]
Answer: 2.72727272......g/cm3^
Explanation:
D = g/cm^3
soo d = 15/5.5