(ab/bc, non-calculator) the position function 2 st t ( ) 4.9 396.9   , gives the height (in meters) of an object that has fallen from a height of 396.9 meters after t seconds. (a) explain why there must exist a time t , 1 2  t  , at which the height of the object must be 382 meters above the ground. (b) find the time at which the object hits the ground. (c) find the average rate of change in s over the intervalt 8,9. include units of measure. explain why this is a good estimate of the velocity at which the object hits the ground. how can this estimate be improved? (d) evaluate: 3 ( ) (3) limt 3 st s  t   . show the work that leads to your answer. include units.