Graphs in practical situations — practice question

A train runs between two stations and is at rest both when it sets off and when it arrives. For the first $30$ seconds, it speeds up uniformly from rest until its speed is $20\text{ m s}^{-1}$; during the following $60$ seconds it continues at a steady $20\text{ m s}^{-1}$; over the final $20$ seconds it decelerates uniformly until it comes to rest.