Thanks Baldric- I didn't see the extra bit tagged on later.
This cannot be a genuine homework question in this form.
There is not enough info- how far apart are they when they start, how long is the chicane, and at what times do they stop?
And we have to assume that after each stop they suddenly move from 0 mph to the the stated speed instantaneously. But if that's the case why does it it refer to 3 separate stopping times for train 2, for example, when you just need the total stoppping time?