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Until a train is a safe distance from the station it must travel at 5 m/s. Once the train is on open track it can speed up to 45 m/s. If it takes a train 8 seconds to reach 45 m/s, what is the acceleration of the train? (Round your answer to the nearest whole number.)
4 m/s2
5 m/s2
6 m/s2
7 m/s2