A train starts from rest and accelerates uniformly at a rate of $$2 m s$$ - $$2 \,for\, 10 s$$. It then maintains a constant speed for $$200 s$$. The brakes are then applied and the train is uniformly retarded and comes to rest in $$50 s$$. Find :$$ (i) $$the maximum velocity reached, $$(ii)$$ the retardation in the last $$50 s$$, $$(iii)$$ the total distance travelled, and $$(iv)$$ the average velocity of the train.