A train is traveling from A to D$.$ Its initial velocity at A is zero. The train takes $5$ min to cover the

distance AB$,2250$ m length and $2\mathrm{.}5$ minutes to cover, the distance BC$,3000$ m in length, on reaching

the station C$,$ the brakes are applied and the train stops $2250$ m beyond, at D $($i$)$ Find the retardation on

CD$,($ii$)$ the time it takes the train to get from A to D$,$ and $($iii$)$ its average speed for the whole distance.