A train moves as follows:
(i) travels with constant velocity 20m/s for 15s,
(ii) then slows down uniformly to 10m/s in the next 5s,
(iii) finally accelerates uniformly to 25m/s in the next 10s.
Calculate the total displacement of the train during the entire 30s.
a) 600m
b) 500m
c) 550m
d) 575m