What is the distance between station a and station b?

[datbert]

Homework Statement

a train starts from station a with a uniform acceleration of 5.00 x 10^-1 m/s^2 (east) and attains full speed after 50.0s. It travels at full speed for 1.20 x 10^2 s, then is brought to rest at station b by the application of the brakes which produces a constant acceleration of -2.50 m/s^2 (east). find the distance between station a and station b

The Attempt at a Solution

i tried adding station a and b's displacements but it didn't add up to 3.75x10^3 m (the answer)

i got station a's displacement by finding vfinal then using d=vft-1/2at^2 and added that to the other displacement and yea didn't work.

 

[Simon Bridge]

Draw the v-t graph - the displacement is the area under the graph.
Note: considering the stations are not moving, both their displacement's are 0.
Station a will be at position x=0m.

In the first stage of the journey, you need to find the final speed.
In the last stage you need to find the time to decelerate to rest.