The speed of a runner increased steadily during the first three seconds of a race. Her speed at half-second intervals is given in the table. Find lower and upper estimates for the distance that she traveled during these three seconds. ft (smaller value) ft (larger value) t (s) 0 0.5 1.0 1.5 2.0 2.5 3.0 v (ft/s) 0 6.7 9.2 14.1 18.8 19.8 20.2