Two trains $$A$$ and $$B$$ leave the same station on parallel lines. Train $$A$$ starts with a uniform acceleration of $1/6$ m$/$s$2$ and attains the speed of $24$ km$/$hr$,$ then stem is reduced to keep the speed constant. Train $$B$$ leaves $40$ seconds after, with uniform acceleration of $1/3$ m$/$s$2$ to attain the maximum speed of $48$ km$/$hr$.$ When will it overtake the train $$A$?$