In a 100 metre sprint, Usain Bolt typically reaches his top speed after the first 60 metres. What is his acceleration over the final 40 metres of the race (in

m/s^2), if he is able to maintain a constant velocity until the finish line? Note: the time taken to run the entire 100 m race was 10.0 s and the time taken to run the final 40 metres was 3.91 s.