At clock time t = 13 sec the depth of water in a container is 54 cm, while at clock time t = 33 sec the depth is 27 cm. Plot the corresponding points on a graph of depth vs. clock time and determine the slope of the straight line segment connecting these points. Explain why this slope represents the average rate at which the water depth changes over this time interval.

For the quadratic function y = f(t) = .015 t² + -2.04 t + 78, determine the average rate of change of y with respect to t, between clock times t = 33 and t = 40.