Atrain engineer started the train from a standstill and sped up to 5 meters per second, she then rounded a corner at a constant speed. she then sped the train up to 10 meters per second on the next straightaway. next, the train chugged around another bend at 10 m/sec, and then its speed slowed to 5 meters per second after coming out of the bend. finally, the train reached the station, and the engineer applied the brakes and brought the engine to a stop. how many times did the train accelerate?