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 (in ft) that she traveled during these three seconds. t (5) 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 19.4 20