3. A skydiver jumps out of a plane that is flying 2500 m above the ground. The skydiver's height above the ground, in metres, after t seconds is /()=2500-4.912. a) Determine the rate of change of the height of the skydiver after 5 s. b) The skydiver's parachute opens at 1000 m above the ground. After how many seconds does this happen? c) What is the rate of change of the height of the skydiver at the time found in part b)