In april 1974, steve prefontaine completed a 10 km race in a time of 27 min, 43.6 s. suppose "pre" was at the 8.13 km mark at a time of 25.0 min. if he accelerated for 60 s and then maintained his increased speed for the remainder of the race. calculate his acceleration over the 60 s interval. assume his instantaneous speed at the 8.13 km mark was the same as his overall average speed up to that time.