Every one of us is all too familiar with the phenomenon of forgetting. Facts that we clearly understood at the time we first learned them sometimes fade from our memory by the time the final exam rolls around. Psychologists have proposed several ways to model this process. One such model is Ebbinghaus' Law of Forgetting, described on page 356. Other models use exponential or logarithmic functions. To develop her own model, a psychologist performs an experiment on a group of volunteers by asking them to memorize a list of 100 related words. She then tests how many of these words they can recall after various periods of time. The average results for the group are shown in the table. Time Words recalled 15 min 63.8 1 h 44.5 8 h 38.1 1 day 33.3 2 days 27.3 24.9 3 days 5 days 22.6 (a) Use a graphing calculator to find a power function of the form y = atb that models the average number of words y that the volunteers remember after t hours. (Round all numerical values to three decimal places.) y = Find an exponential function of the form y = abt to model the data. (Round all numerical values to three decimal places.) y =