The train, approaching the station at a speed of 90 km / h, begins to brake evenly. What is the shortest time for the train

The train, approaching the station at a speed of 90 km / h, begins to brake evenly. What is the shortest time for the train to decelerate to a full stop, safe for passengers sleeping on the upper bins? Shelf friction coefficient 0.2. At what distance to the station should you start braking?

ma = Ftr = 0.2 mg ..
a = 0.2g. = 2 m / s2 …
90 km / h. = 25 m / s.
decision:
v = at … t = v / a = 12.5 s ..
s = at “2/2 = 156 meters.
answer: 156 meters.