A sprinter performs a 100 m dash. During the initial s25 = 25m he accelerates, obtaining an average acceleration a = 2.3 m/s2 . After the first 25m he holds the velocity constant. Between the 90m mark and the finish line he has an average acceleration of af = -0.1 m/s2 . a) What is his final velocity vf at the end of the first 25 meters? (2 pts.) b) What is his total race time? (2 pts.) c) What is his average velocity v for the 100 m dash