Ingrid is docking a motorboat. She turns off the power and lets the boat coast toward the dock. The distance, d, in meters, between the boat and the dock as a function of time, t, in seconds, is given by d(t)=-7t+70/t + 4,

Question

Ingrid is docking a motorboat. She turns off the power and lets the boat coast toward the dock. The distance, d, in meters, between the boat and the dock as a function of time, t, in seconds, is given by d(t)=-7t+70/t + 4, 
0 ≤ t ≤ 10
a) What is the average velocity of the boat during the time interval from when Ingrid turns the boat off to when it meets the dock? 
b) Determine the velocity of the boat when Ingrid turns off the power, to one decimal place. 
c) Determine the velocity of the boat when it meets the dock, to one decimal place. 
d) Sketch a graph of the function. On the same set of axes, sketch a graph of the speed of the boat in relation to the time.