6. The students in a physics class are performing an experiment to determine the acceleration due to gravity. They drop water balloons from the top of a building and estimate the time at which the balloons hit the ground. After analyzing all of their data, the produce the model h(t)=-52 + 30 to model the height of a balloon in metres 1 seconds after it has been dropped. What is the best estimate for the instantaneous rate of change in the height of a balloon I s after it has been dropped? a. -20 m/s b. -10 m/s c. -5 m/s d. 5 m/s